PURPOSE: To aim at the compactification of a generator on the whole as well as improvements in transportability and stability, by disposing an engine's crankshaft and a generator's rotary shaft coaxially along a vertical direction, while setting up the generator on the downside of the engine.

CONSTITUTION: A crankshaft 3 of an engine 1 and a rotary shaft 13 of a generator 8 both are disposed coaxially along a vertical direction. Moreover, the generator 8 is made to be weighter than the engine 1 and disposed on the underside of the engine 1. Doing like this, a plane area of projection can be held down to be yet smaller so that compactification on the whole and improvements in transportability and stability can be all actualized.