An in-wheel motor includes a wheel disc, a wheel hub, a case, a motor, a planetary gear and a shaft. The wheel disc is connected to the wheel hub. The planetary gear is connected to the motor's rotor. The case includes subcases and a diaphragm. One subcase is arranged to have a side portion closer to the vehicle's body and accommodates the motor and the planetary gear. The motor and the planetary gear are adjacently arranged and fixed to one subcase. The other subcase is arranged closer to the wheel disc and fixed at a plane perpendicular to the shaft by a screw to one subcase.