An object of the present invention is to provide an anticancer drug capable of treating cancer by finding a target molecule specifically expressed in cancer cells and by specifically acting on the target molecule, and to provide a cancer testing method including a step of measuring the target molecule in a sample. The present invention provides an anticancer drug containing, as an active ingredient thereof, an anti-transmembrane protein 180 (TMEM-180) antibody or an antigen-binding fragment thereof. In addition, the present invention provides a cancer testing method including a step of measuring the amount of TMEM-180 in a sample collected from a subject.