A rear cargo bed structure of a multipurpose vehicle is provided. The multipurpose vehicle includes a vehicle frame unit, a steering device connected to the vehicle frame unit and operable to control a moving direction of the multipurpose vehicle, a front wheel assembly mounted to a front end of the vehicle frame unit, a seat portion mounted on the vehicle frame unit to receive a driver and a passenger to sit thereon, a rear wheel assembly mounted to a rear end of the vehicle frame unit, and a vehicle cover unit set on and covering a periphery of the vehicle frame unit. A rear cargo bed in the form of a flat surface is arranged on a rear frame portion of the vehicle frame unit. As such, the performance of the multipurpose vehicle for carrying cargo is improved.