A motor-driven actuator is provided that can prevent generation of hitting sound due to rattling of an output shaft of a motor. The motor-driven actuator is equipped with a motor with an output shaft, worm attached to the output shaft, and rotation member with a worm wheel engaging with the worm inside a case, wherein a bearing member equipped with a regulating face adjacent to a top end of said output shaft and intergrading by biasing force of a spring in a manner said regulating face pushes the top end of said output shaft into the direction of thrust is provided.