A lower part structure in a vehicle body rear part has a rear suspension frame disposed in rear of a fuel tank and in front of a spare tire and has a mechanism for causing jump up of the rear part of the spare tire under load application from the vehicle rear. The lower part structure is configured so that the center in the vertical direction of the front part of the spare tire is located so as to lap on the extension line of vertical width of a frame in the vehicle width direction of the rear suspension frame, and when the spare tire is moved to the vehicle front by a load applied from the vehicle rear, the spare tire comes into contact with the rear suspension frame directly or indirectly, whereby the rear part of the spare tire is pushed up with the rear suspension frame side being the center, and is turned in the longitudinal direction.