Disclosed is a gas pressure actuator whose actuator body has a cylinder, a piston and a gas generator in which a powder is loaded, and the gas generator is positioned at an end portion of the cylinder. The gas generator injects a high pressure gas into the cylinder by the combustion of the powder, thereby moving the piston. The actuator body is provided with a coating which covers the entire actuator body from outside. The coating is a resin coating having electrically insulating, waterproof, and dustproof characteristics.