It is intended to provide an anti-EphA4 antibody or an EphA4-binding fragment thereof which is capable of binding to EphA4 and inhibiting the binding between EphA4 and its ligand, and a pharmaceutical composition comprising the anti-EphA4 antibody or the EphA4-binding fragment thereof as an active ingredient. A mouse anti-EphA4 antibody having binding affinity for EphA4 was obtained, and the sequences of complementarity-determining regions (CDRs) of the mouse anti-EphA4 antibody were identified. This allowed for preparation of a humanized antibody comprising the CDR sequences of the mouse anti-EphA4 antibody in heavy chain variable region and light chain variable region.