A power generator 1 includes a magnetostrictive rod 2 through which lines of magnetic force pass in an axial direction thereof, a beam member 73 having a function of generating stress in the magnetostrictive rod 2, and a coil 3 arranged so that the lines of magnetic force pass inside the coil 3 in an axial direction of the coil 3. The beam member 73 is arranged along the magnetostrictive rod 2 and configured to allow one end portion and the other end portion of the magnetostrictive rod 2 to approach to each other to generate compressive stress in the magnetostrictive rod 2. Further, in the power generator 1, it is preferable that a gap between the beam member 73 and the magnetostrictive rod 2 on the side of the one end portion of the magnetostrictive rod 2 is larger than a gap between the beam member 73 and the magnetostrictive rod 2 on the side of the other one end portion of the magnetostrictive rod 2 in a side view.