A piezoelectric actuator having a frame portion includes a drive shaft for frictional engagement with an engageable barrel arm of a lens unit. First and second piezoelectric elements are supported on the frame portion, and provided with first and second ends of respectively the drive shaft. A drive pulse generator supplies the piezoelectric elements with a drive signal to expand or contract the piezoelectric elements, and moves the engageable barrel arm in an axial direction by an alternately repeating sequence of shifting the drive shaft at low and high speeds in the axial direction. In the shifting at the high speed, the piezoelectric elements shift the drive shaft in a backward direction quickly, to move the drive shaft in the backward direction relative to the engageable barrel arm being stationary with inertial force.