A shift range switching device is provided to a shift-by-wire system for an automatic transmission device. The shift range switching device includes a range switching unit for switching a shift range of the automatic transmission device between a P range and the other range. The shift range switching device further includes an actuator including an electric motor and a reduction device. The reduction device transmits driving force of the electric motor to the range switching unit for actuating the range switching unit as instructed. The reduction device has a variable reduction ratio. The reduction device transmits the driving force in switching of the shift range from the P range to the other range at a reduction ratio, which is greater than a reduction ratio in switching of the shift range from the other range to the P range.