To provide a steam generator in a cylinder of an internal combustion engine using liquid fuel.

The steam generator is formed by providing: an electronic control distilled water injection system in addition to an electronic control fuel injection system; and an ignition system in the cylinder of the internal combustion engine using liquid fuel. The liquid fuel is injected in the cylinder, ignition and explosion are carried out, distilled water of an adequate amount is injected in generated fuel explosion heat to carry out vaporization, and a piston is moved by combining explosion energy of the liquid fuel and expansion energy of vaporization. The liquid fuel is saved on.