To provide a method of continuing the power supply by continuing the operation of a device, when an internal combustion engine is used as the drive source of the power generation system of the device, if the range of the inclination of the device is such that the seizure will not occur, instead of the internal combustion engine being simply stopped, even when the device is inclined and the inclination exceeds a prescribed range, in order to solve a problem that the lubricant of the internal combustion engine will not be sufficiently fed or will not be fed at all to cause the seizure if the device is set on a place with a large inclination such as on the sea.

In the engine for power generation to be used in the device whose posture is largely changed to be inclined, the operation condition of the engine is controlled to be in the off state, in the idling state, or in the normal rotation state by a signal from a detecting part for detecting the inclination of the device.