To provide a starting method for an unmanned helicopter engine started by a miniature and light self-starter even an engine having much displacement and restrain the increase of the total weight of the unmanned helicopter loading the self-starter.

In this starting method for an unmanned helicopter 1 engine, a decompressor 6 of one cylinder of a plural-cylinder engine 2 is closed, and the decompressors 6 of the remainder cylinders are opened to ignite and start only one cylinder of the engine 2 based on the jump timing for a self-starter 7 loaded on an unmanned helicopter; and then the starter 7 is stopped, and also the decompressors 6 of the remainder cylinders are closed, and the remainder cylinders of the engine 2 are ignited and started by driving a connected crank shaft.