It is an object of the present invention to provide an antibody specifically binding to GPR20-positive tumor cells such as GIST, a pharmaceutical product comprising the antibody and having therapeutic effects on a tumor, a method for treating a tumor using the aforementioned pharmaceutical product, and the like. It is another object of the present invention to provide an anti-GPR20 antibody having internalization activity, an antibody-drug conjugate containing the antibody, and the like.
