An object of the invention is to find a cancer-associated gene to be used as an index for detecting canceration of cells and degree of malignancy of cancer, so as to to provide a method for detecting cancer using the cancer-associated gene as an index and provide a method of suppressing/treating cancer using the cancer-associated gene as essential part. According to the present invention, specific genes which are amplified or deleted in bile duct cancer as compared with normal cell have been collectively found, and a method for detecting cancer using amplification or deletion of these cancer-associated genes as an index is provided. Further, cancer can be suppressed by introducing a gene which is deleted in cancer cells amond these cancer-associated genes into cancer and inhibiting the transcription product of the gene amplified.