A leaf spring 4 constituting an elastic member one end of which is fixed to a foundation 6, and other end of which is brought into contact with a laminating type piezoelectric element 2 or a driven member 5 is constituted such that a thickness is thinned from a side of the foundation 6 to a side of the laminating type piezoelectric element 2 to make a moment of inertia smaller on a side of a portion of other end held by the laminating type piezoelectric element 2 than a portion on one end side fixed to the foundation 6. Further, a strain gage sensor 8 is attached to a side face 4a of the leaf spring 4 constituting one face of one end of the leaf spring 4 proximate to the laminating type piezoelectric element 2 orthogonal to a direction of elongating and contracting the laminating type piezoelectric element 2 constituting a side of the driven member 5.