An electric motor includes a stator, a rotor provided rotatably about a predetermined rotational axis line relative to the stator, a cooling fan configured to rotate an impeller through a fan motor fixed to the stator, and a coupling unit configured to detachably couple the rotor and the impeller of the cooling fan. The coupling unit couples the rotor and the impeller while the fan motor is stopped, and decouples the rotor and the impeller after the fan motor starts.