The electric motor with a reverse input cutoff clutch has an output shaft. The output shaft is configured by connecting a first shaft and a second shaft that are coaxially arranged with each other via the reverse input cutoff clutch. The second shaft is rotatably supported to a housing by one radial bearing. The reverse input cutoff clutch has a function that, when rotational torque is inputted to the first shaft, transmits the rotational torque inputted to the first shaft to the second shaft, and when rotational torque is reversely inputted to the second shaft, completely cuts off the rotational torque reversely inputted to the second shaft, and does not transmit the rotational torque to the first shaft, or transmits a part of the rotational torque to the first shaft, and cuts off the remaining part.