There is provided the use of a substituted diphenylamine compound of general formula I in the preparation of an antitumor agent. The compounds of general formula I have good antitumor activity which is particularly suitable for treating or alleviating cancers caused by tumor cells of human tissues or organs. The cancer is preferably colon cancer, lymph node cancer, lung cancer, esophageal cancer, breast cancer, cancer of the central nervous system, melanoma, ovarian cancer, cervical cancer, kidney cancer, leukemia, prostate cancer, pancreatic cancer, bladder cancer, Examples include rectal cancer, osteosarcoma, pharyngeal cancer, and gastric cancer. The structure of the compound of general formula I is shown in formula (I).抗腫瘍薬の調製における一般式Ｉの置換ジフェニルアミン化合物の使用を提供する。一般式Ｉの化合物は、特に、人体の組織又は臓器の腫瘍細胞によって引き起こされる癌を治療又は緩和するために適する良好な抗腫瘍活性を有する。癌は、好ましくは、結腸癌、リンパ節癌、肺癌、食道癌、乳癌、中枢神経系の癌、黒色腫、卵巣癌、子宮頸癌、腎臓癌、白血病、前立腺癌、膵臓癌、膀胱癌、直腸癌、骨肉腫、咽頭癌又は胃癌などである。一般式Ｉの化合物の構造は、式（Ｉ）に示される。
