Lower structure of vehicle body rear portion

A lower structure of a vehicle body rear portion, includes: a spare tire housing formed in a rear floor; a cross member joining paired side frames, and being provided at a location frontward of the housing; a reinforcement for a hook, being arranged at a center of the housing; and a bumper member provided at a rear end of the vehicle body, in which a front side of the reinforcement is attached to the cross member, the reinforcement forms a closed cross section so that the closed cross section is larger at a rear side than at a front side, the reinforcement includes front and rear portions obtained by dividing the reinforcement at a location corresponding to a center of a spare tire, and an upper side of a rear end of the rear portion is arranged below the bumper member and overlaps with the bumper member (FIG. ).