A power generation unit (1A) for converting an externally applied force into electricity comprises piezoelectric elements (22, 23), and a central spacer (24) and a peripheral spacer (25) provided, respectively, between a plurality of stacked piezoelectric elements (22, 23) or provided, respectively, between a plane for pressing the piezoelectric elements (22, 23) and the piezoelectric elements (22, 23) in order to form the deformation space of the piezoelectric elements (22, 23) and to transmit a deformation force to the piezoelectric elements. For example, the piezoelectric elements (22, 23) are fixed, respectively, to the both sides of a flexible diaphragm (21), columnar central spacers (24) are arranged on the piezoelectric elements (22, 23) and an annular peripheral spacer (25) is arranged on the diaphragm (21).