The present invention discloses reshaped antibody to human medulloblastoma cells comprising: (A) an L chain comprising: (1) a human L chain C region, and (2) an L chain V region comprising human L chain FRs and L chain CDRs of mouse monoclonal antibody ONS-M21 to human medulloblastoma cells; and, (B) an H chain containing: (1) a human H chain C region, and (2) an H chain V region comprising human H chain FRs and H chain CDRs of mouse monoclonal antibody ONS-M21 to human medulloblastoma cells. Since the majority of this reshaped human antibody is derived from a human antibody and mouse CDRs have a low level of antigenicity, the reshaped human antibody of the present invention has a low level of antigenicity in humans, and is therefore expected to be useful as a therapeutic agent and diagnostic tool for brain tumors such as medulloblastoma which strongly express antigen that is recognized by this antibody.