To provide an extremely clean engine capable of acquiring a mechanical power by taking as a fuel a liquid such as water with a relatively simple device.

An engine is equipped with a cylinder 2 provided with a space taken as an expansion chamber 1 therein and a piston 3, a local heater 4 for carrying out local heating in the expansion chamber 1, an injection nozzle 5 for supplying water to a locally heated part 7 of the local heater 4 and a discharge passage 6 for discharging water from the expansion chamber 1. In the local heater 4, a coil 14 to which high-frequency current is applied is wound on a core member 13 made of an insulating material having high permeability. A conductive member 7 taken as the locally heated part 7 is provided to an end of the core member 13.