The present invention addresses the problem of providing: an antibody having an internalization activity of binding to CDH6； an antibody-drug conjugate consisting of the aforesaid antibody and a drug having an antitumor activity； a medicine using the antibody-drug conjugate, said medicine having a therapeutic effect on tumors； a method for treating tumors using the antibody, the antibody-drug conjugate or the medicine； etc. Provided are: an anti-CDH6 antibody having an internalization activity； an antibody-drug conjugate consisting of the aforesaid antibody and a drug having an antitumor activity； and a medicine and a method for treating tumors using the same.
