To enable use of a small-output electric motor by reducing the driving torque of the electric motor when switching an automatic transmission from a P range to a R range.

An output shaft 14 is turned by the electric motor 4 through a reduction gear mechanism 7, and the gear shift range of the automatic transmission is switched in response to the angle of turning. A peripheral side of the output shaft 14 is provided with a cylindrical lever 16 for abutting on a driven gear 13 within the turning range corresponding to a range between the P range and the R range and an energizing spring 17 for energizing the cylindrical lever 16 toward the driven gear 13. With this structure, when switching the automatic transmission from the P range to the R range, the driving torque of the electric motor 4 requested to output a large torque when switching can be reduced by the energizing spring 17. Use of the electric motor 4 having a small output is thereby enabled, and miniaturization and reduction of the cost can be aimed.