To provide an actuator which stably and accurately moves a driven member by providing a second piezoelectric element which secures or releases friction engagement between a driving member and a driven member fitted to first piezoelectric elements.

The actuator 30 which drives lens frames 18, 20 in an optical axis direction comprises the first piezoelectric elements 32A, 32B for driving, the second piezoelectric element 32C for engagement, the driving members 34A, 34B, and a presser spring 36. The piezoelectric elements 32A, 32B and the driving members 34A, 34B are arranged at both sides of the driven board 26 with the board placed therebetween, and a spacing between the driving members 34A, 34B is extended or shortened by the piezoelectric element 32C. The friction engagement between the driving members 34A, 34B and the driven board 26 is secured or released by the piezoelectric elements 32C.