A vehicle body rear part includes a side sill, a rear side frame, a cross member, a trailing arm, an arm attachment bracket, and a close plate. In the trailing arm, a front end part is swingably supported via a mount member at a front region of the rear side frame. The arm attachment bracket is fixed into a cross section of the rear side frame and has a fixation nut with which the mount member is fastened and fixed. The bracket reinforcement member reinforces the arm attachment bracket. The close plate closes an opening on an upper side of the front region of the rear side frame. End parts on both sides in the vehicle width direction of the bracket reinforcement member are joined to the side sill and the cross member, and an upper part of the bracket reinforcement member is joined to the close plate.