The invention relates to a car body rear structure, and the number of parts of the car body rear structure is reduced. The car body rear structure is provided with a rear mudguard (40) on the rear part of the car, the rear mudguard (40) is provided with a mudguard main body (41) covering the upper part of a rear wheel (4) and an armrest (42) for a passenger to hold, and the armrest (42) and the mudguard main body (41) are integrally molded.