A vehicle body structure in which a hollow-section crossmember is attached to rear end portions of right and left center frame members is provided. Right and left extension members extending rearward are joined to the rear end portions of the right and left center frame members. The crossmember is joined to the tops of the right and left extension members. Right and left reinforcing plates are provided in a hollow space of the crossmember at portions at which the extension members are joined to the crossmember. The right and left reinforcing plates are supported on the right and left extension members, whereby the crossmember is firmly supported on the rear end portions of the center frame members and is increased in rigidity.