| 2020 |
| 07/30 | （IR情報）15:30 自己株式の消却に関するお知らせ |
| 07/30 | （IR情報）15:30 当社株式の上場廃止のお知らせ |
| 07/29 | 110 | 110 | 107 | 107 | -4.46% | 1,280,100 | 438億4543万 | -6.14% |
| 07/28 | 112 | 113 | 110 | 112 | 0% | 778,500 | 458億9428万 | -2.61% |
| 07/27 | 111 | 113 | 110 | 112 | -0.88% | 569,000 | 458億9428万 | -2.61% |
| 07/22 | 114 | 115 | 113 | 113 | 0% | 385,000 | 463億405万 | -1.74% |
| 07/21 | 115 | 115 | 112 | 113 | -2.59% | 385,400 | 463億405万 | -1.74% |
| 07/20 | 115 | 116 | 114 | 116 | 0% | 467,100 | 475億3336万 | 0% |
| 07/17 | 119 | 119 | 114 | 116 | -2.52% | 680,300 | 475億3336万 | 0% |
| 07/16 | 119 | 121 | 118 | 119 | +1.71% | 1,219,500 | 487億6267万 | +2.59% |
| 07/15 | 116 | 119 | 116 | 117 | +1.74% | 430,800 | 479億4313万 | +0.86% |
| 07/14 | 114 | 116 | 113 | 115 | +0.88% | 495,100 | 471億2359万 | -1.71% |
| 07/13 | 113 | 116 | 113 | 114 | +3.64% | 277,000 | 467億1382万 | -2.56% |
| 07/10 | 112 | 113 | 110 | 110 | -2.65% | 359,400 | 450億7474万 | -5.98% |
| 07/09 | 114 | 115 | 112 | 113 | -2.59% | 486,000 | 463億405万 | -4.24% |
| 07/08 | 112 | 116 | 112 | 116 | +1.75% | 302,100 | 475億3336万 | -1.69% |
| 07/07 | 114 | 115 | 112 | 114 | -1.72% | 585,200 | 467億1382万 | -4.2% |
| 07/06 | 114 | 116 | 113 | 116 | +1.75% | 341,300 | 475億3336万 | -1.69% |
| 07/03 | 114 | 115 | 112 | 114 | 0% | 475,800 | 467億1382万 | -3.39% |
| 07/02 | 114 | 114 | 111 | 114 | +0.88% | 450,100 | 467億1382万 | -3.39% |
| 07/01 | 115 | 115 | 112 | 113 | -0.88% | 449,600 | 463億405万 | -4.24% |
| 06/30 | 114 | 117 | 114 | 114 | +1.79% | 594,000 | 467億1382万 | -3.39% |
| 06/29 | 114 | 114 | 111 | 112 | -3.45% | 570,300 | 458億9428万 | -5.08% |
| 06/26 | （IR情報）15:30 主要株主の異動に関するお知らせ |
| 06/26 | （IR情報）15:30 支配株主等に関する事項について |
| 06/26 | （IR情報）15:30 株式給付信託制度(BBT)廃止についてのお知らせ |
| 06/26 | （IR情報）15:30 株式交換契約に関する定時株主総会の承認可決についてのお知らせ |
| 06/26 | 115 | 117 | 114 | 116 | +1.75% | 450,300 | 475億3336万 | -1.69% |
| 06/25 | 116 | 116 | 114 | 114 | -1.72% | 286,300 | 467億1382万 | -2.56% |
| 06/24 | 119 | 119 | 116 | 116 | -3.33% | 554,100 | 475億3336万 | -0.85% |
| 06/23 | 120 | 121 | 117 | 120 | +1.69% | 993,900 | 491億7244万 | +3.45% |
| 06/22 | 117 | 119 | 117 | 118 | 0% | 299,300 | 483億5290万 | +2.61% |
| 06/19 | 120 | 120 | 117 | 118 | -0.84% | 900,000 | 483億5290万 | +2.61% |
| 06/18 | 120 | 121 | 118 | 119 | -0.83% | 553,500 | 487億6267万 | +4.39% |
| 06/17 | 123 | 123 | 120 | 120 | -4% | 741,900 | 491億7244万 | +7.14% |
| 06/16 | 121 | 125 | 121 | 125 | +6.84% | 807,500 | 512億2129万 | +12.61% |
| 06/15 | 118 | 122 | 117 | 117 | -0.85% | 1,093,600 | 479億4313万 | +6.36% |
| 06/12 | 119 | 120 | 117 | 118 | -2.48% | 802,000 | 483億5290万 | +8.26% |
| 06/11 | 124 | 124 | 121 | 121 | -3.97% | 1,341,300 | 495億8221万 | +12.04% |
| 06/10 | 123 | 128 | 123 | 126 | 0% | 1,283,300 | 516億3106万 | +18.87% |
| 06/09 | 127 | 127 | 125 | 126 | 0% | 988,100 | 516億3106万 | +20% |
| 06/08 | 127 | 128 | 124 | 126 | +2.44% | 1,257,400 | 516億3106万 | +22.33% |
| 06/05 | 125 | 125 | 122 | 123 | +0.82% | 529,800 | 504億175万 | +20.59% |
| 06/04 | 122 | 126 | 121 | 122 | +0.83% | 1,617,900 | 499億9198万 | +22% |
| 06/03 | 117 | 123 | 116 | 121 | +7.08% | 2,493,800 | 495億8221万 | +22.22% |
| 06/02 | 113 | 114 | 112 | 113 | 0% | 794,700 | 463億405万 | +15.31% |
| 06/01 | 113 | 115 | 113 | 113 | 0% | 455,000 | 463億405万 | +16.49% |
| 05/29 | 115 | 116 | 113 | 113 | -3.42% | 1,077,400 | 463億405万 | +17.71% |
| 05/28 | 114 | 118 | 114 | 117 | +3.54% | 1,968,000 | 479億4313万 | +23.16% |
| 05/27 | 109 | 113 | 109 | 113 | +3.67% | 1,038,600 | 463億405万 | +20.21% |
| 05/26 | 106 | 110 | 105 | 109 | +5.83% | 1,920,800 | 446億6497万 | +17.2% |
| 05/25 | 101 | 104 | 101 | 103 | +4.04% | 930,400 | 422億634万 | +11.96% |
| 05/22 | （IR情報）15:30 株式交換契約承認、取締役候補者選任及び補欠監査役候補者選任に関するお知らせ |
| 05/22 | 103 | 103 | 98 | 99 | -2.94% | 993,800 | 405億6726万 | +8.79% |
| 05/21 | 102 | 104 | 101 | 102 | 0% | 594,500 | 417億9657万 | +13.33% |
| 05/20 | 101 | 103 | 100 | 102 | +0.99% | 719,200 | 417億9657万 | +13.33% |
| 05/19 | 98 | 103 | 98 | 101 | +5.21% | 4,099,000 | 413億8680万 | +13.48% |
| 05/18 | 97 | 97 | 95 | 96 | 0% | 1,405,800 | 393億3795万 | +9.09% |
| 05/15 | 98 | 99 | 92 | 96 | +10.34% | 2,845,700 | 393億3795万 | +10.34% |
| 05/14 | （IR情報）15:30 業績予想と実績との差異に関するお知らせ |
| 05/14 | （IR情報）15:30 三井化学によるアークの簡易株式交換による完全子会社化及び三井化学による完全子会社の吸収合併(簡易合併・略式合併)に関するお知らせ |
| 05/14 | （IR情報）15:30 2020年3月期決算短信〔日本基準〕(連結) |
| 05/14 | （IR情報）15:30 親会社及び主要株主である筆頭株主の異動に関するお知らせ |
| 05/14 | 90 | 92 | 86 | 87 | -3.33% | 356,000 | 356億5002万 | +1.16% |
| 05/13 | 89 | 91 | 88 | 90 | +1.12% | 310,000 | 368億7933万 | +5.88% |
| 05/12 | 89 | 90 | 89 | 89 | -1.11% | 71,700 | 364億6956万 | +4.71% |
| 05/11 | 90 | 91 | 89 | 90 | 0% | 165,000 | 368億7933万 | +7.14% |
| 05/08 | 90 | 90 | 88 | 90 | +1.12% | 240,800 | 368億7933万 | +8.43% |
| 05/07 | 89 | 90 | 88 | 89 | +1.14% | 284,200 | 364億6956万 | +7.23% |
| 05/01 | 90 | 90 | 87 | 88 | -1.12% | 292,700 | 360億5979万 | +7.32% |
| 04/30 | 90 | 90 | 89 | 89 | -1.11% | 180,900 | 364億6956万 | +8.54% |
| 04/28 | 89 | 90 | 88 | 90 | +3.45% | 214,400 | 368億7933万 | +11.11% |
| 04/27 | 87 | 88 | 86 | 87 | 0% | 156,300 | 356億5002万 | +8.75% |
| 04/24 | 88 | 89 | 86 | 87 | -2.25% | 230,500 | 356億5002万 | +10.13% |
| 04/23 | 89 | 90 | 88 | 89 | +1.14% | 265,000 | 364億6956万 | +14.1% |
| 04/22 | 89 | 90 | 87 | 88 | -1.12% | 273,300 | 360億5979万 | +14.29% |
| 04/21 | 89 | 90 | 88 | 89 | 0% | 220,400 | 364億6956万 | +15.58% |
| 04/20 | 89 | 90 | 87 | 89 | 0% | 175,700 | 364億6956万 | +17.11% |
| 04/17 | 89 | 90 | 88 | 89 | +2.3% | 402,300 | 364億6956万 | +18.67% |
| 04/16 | 86 | 88 | 85 | 87 | +2.35% | 230,400 | 356億5002万 | +17.57% |
| 04/15 | 86 | 86 | 83 | 85 | 0% | 274,700 | 348億3048万 | +16.44% |
| 04/14 | 85 | 86 | 84 | 85 | +2.41% | 415,100 | 348億3048万 | +16.44% |
| 04/13 | 83 | 84 | 82 | 83 | -1.19% | 346,100 | 340億1094万 | +15.28% |
| 04/10 | 84 | 84 | 80 | 84 | +2.44% | 330,000 | 344億2071万 | +16.67% |
| 04/09 | 81 | 82 | 79 | 82 | +3.8% | 229,800 | 336億117万 | +13.89% |
| 04/08 | 77 | 79 | 75 | 79 | +3.95% | 287,100 | 323億7186万 | +9.72% |
| 04/07 | 75 | 76 | 75 | 76 | +4.11% | 241,600 | 311億4254万 | +5.56% |
| 04/06 | 71 | 73 | 71 | 73 | +4.29% | 322,300 | 299億1323万 | +1.39% |
| 04/03 | 71 | 72 | 68 | 70 | 0% | 298,100 | 286億8392万 | -2.78% |
| 04/02 | 72 | 72 | 69 | 70 | -1.41% | 310,000 | 286億8392万 | -4.11% |
| 04/01 | 73 | 74 | 71 | 71 | -2.74% | 168,800 | 290億9369万 | -2.74% |
| 03/31 | 76 | 77 | 73 | 73 | -2.67% | 292,100 | 299億1323万 | -1.35% |
| 03/30 | 76 | 77 | 71 | 75 | -3.85% | 392,500 | 307億3277万 | 0% |
| 03/27 | 76 | 78 | 75 | 78 | +4% | 248,200 | 319億6209万 | +4% |
| 03/26 | 74 | 76 | 74 | 75 | +2.74% | 301,300 | 307億3277万 | -1.32% |
| 03/25 | 70 | 74 | 70 | 73 | +7.35% | 301,100 | 299億1323万 | -3.95% |
| 03/24 | 67 | 69 | 67 | 68 | +4.62% | 214,000 | 278億6438万 | -11.69% |
| 03/23 | 64 | 67 | 61 | 65 | +1.56% | 343,700 | 266億3507万 | -16.67% |
| 03/19 | 67 | 68 | 63 | 64 | -3.03% | 226,500 | 262億2530万 | -18.99% |
| 03/18 | 68 | 70 | 66 | 66 | -2.94% | 195,800 | 270億4484万 | -17.5% |
| 03/17 | 62 | 69 | 61 | 68 | +6.25% | 324,500 | 278億6438万 | -16.05% |
| 03/16 | 65 | 67 | 63 | 64 | -1.54% | 209,700 | 262億2530万 | -21.95% |
| 03/13 | 65 | 68 | 62 | 65 | -4.41% | 626,700 | 266億3507万 | -21.69% |
| 03/12 | 67 | 71 | 66 | 68 | -1.45% | 409,700 | 278億6438万 | -19.05% |
| 03/11 | 71 | 75 | 69 | 69 | -4.17% | 319,700 | 282億7415万 | -18.82% |
| 03/10 | 69 | 75 | 66 | 72 | -2.7% | 903,900 | 295億346万 | -16.28% |
| 03/09 | 77 | 78 | 73 | 74 | -7.5% | 320,100 | 303億2300万 | -14.94% |
| 03/06 | 80 | 81 | 80 | 80 | -1.23% | 206,200 | 327億8163万 | -9.09% |
| 03/05 | 82 | 82 | 81 | 81 | +1.25% | 144,400 | 331億9140万 | -7.95% |
| 03/04 | 79 | 82 | 79 | 80 | 0% | 237,600 | 327億8163万 | -10.11% |
| 03/03 | 83 | 84 | 80 | 80 | 0% | 251,200 | 327億8163万 | -10.11% |
