To realize a deformation measuring device capable of simply detecting a bending deformation in a flexible object, in such a state that a strain component is removed in the direction of axial force.

The deformation measuring device is equipped with a measuring section 5 and a pair of piezo-electric films which are two piezo-electric films 1a, 1b being in close contact with the surface of the object and deforming while following the bending deformation in the surface of the object. The piezo-electric films 1a, 1b are laminated such that their extension directions are identical to each other. The measuring section 5 measures a curvature change in the object, based on a difference signal of electromotive forces of respective piezo-electric films 1a, 1b caused by the bending deformation in the object.