In order to provide an actuator having great driving force and high impact resistance, an actuator of the present invention has a driving shaft 5 that can be vibrated in the shaft direction by a piezoelectric device 4 provided at its one end and a moving member 6 that is friction-engaged with the driving shaft 5 and moves on the driving shaft 5 due to the vibration of the driving shaft 5. The driving shaft 5 has two parallel shaft sliding faces 5a on its surface. The moving member 6 has two moving member sliding faces 7e, 8e that are in slide-contact with the shaft sliding faces 5a. The moving member 6 is friction-engaged with the driving shaft 5 such that the moving member sliding faces 7e, 8e clamp the shaft sliding faces 5a.