To get both of large driving force and long stroke at the same time though it is small-sized, in an actuator which gives driving force.

This actuator is equipped with a driving force generator 3 which generates driving force and an operating part 5 which operates by this driving force. The above driving force generator 3 is equipped with one hand of two containers 9 and 11 which are charged with liquid L, being made to communicate with each other, and a suction means 23 which mutually sucks a pair of wall parts 13 and 15 opposed to each other out of one container 9. It pushes out the above liquid L within one container 9 into the other container 11, based on the relative shift of the above paired wall parts 13 and 15 by the above suction means 23. The above operating part 5 consists of the other container 11 which has an operating wall part 25 that is displaced, interlocking with the inflow of the above liquid L pushed out of one container 9. The above operating wall part 25 is smaller than the area of the above wall face parts 13 and 15.