In order to easily and accurately measure the cogging torque of an electric motor, the present invention includes a dynamometer connected to an electric motor, a torque sensor adapted to measure the torque of the electric motor, and a cogging torque measurement motor for measuring the cogging torque of the electric motor, and is configured such that when measuring the cogging torque of the electric motor, the electric motor, the dynamometer, and the cogging torque measurement motor are connected.