A linear power generator has a gas pressure cylinder structure which causes reciprocating motion of a piston in an axial direction by supplying a high-pressure gas alternately to a left gas chamber and a right gas chamber of a cylinder which includes an electromotive coil, and alternately applying a gas pressure in the left gas chamber and a gas pressure in the right gas chamber to the piston which includes a permanent magnet in the cylinder, and which induces power generation of the electromotive coil by way of reciprocating motion of the piston which has the permanent magnet in the axial direction. The linear power generator encourages movement of the piston by supplying a first high-pressure gas into the left gas chamber and the right gas chamber, and keeps moving the piston by supplying a second high-pressure gas for supplementing the first high-pressure gas into the left gas chamber and the right gas chamber.