To suppress frictional resistance force at the time of normal rotation, and to generate a desired frictional resistance force, when inverse torque is applied from a worm wheel side to a motor shaft side.

A motor 10 with worm reducer is so constructed that a worm 17 is provided at one end of the motor shaft 16 supported in the housing 11, where the worm wheel 18 is engaged with the worm 17, and an end spacer 30 is provided at an axial end face of the motor shaft 16. Four frictional force adjusting projections 34 are formed on the slidable contact face 33 of the end spacer 30 on the housing side 11. A gently sloped portion 36 is formed on one side of each frictional force adjusting projection 34 in the circumferential direction and a steeply sloped portion 35 is formed on the opposite side. A flat portion 37 is formed between the top of each gently sloped portion 36 and the top of the corresponding steeply sloped portion 35. The frictional force adjusting projections suppresses frictional resistance force, at normal rotation and generates a large frictional resistance force, when reverse torque is applied from the worm wheel to the motor shaft.