The present invention relates to a cancer-cell-specific polymer compound containing a photosensitizer for photodynamic therapy and having a surface to which an antibody against a cancer-cell-specific antigen binds. An object of the present invention is to provide a photodynamic therapeutic agent that can reach the cancer tissue at a low concentration via active targeting and makes complications (e.g., sunlight hypersensitivity) associated with photodynamic therapy unlikely to occur.
