To gain a fitting placement and shape for an internal combustion engine with a rotary valve, and a fitting shape of piston at that time.

Rotary valves 1, 2 are attached to the edges of cylinders. At that time, the shape of rotary valves are changed into a Japanese-drum or drum shape, or the shape of a piston 11 is sank from a plug or a fuel injector into spherical. Thus, by attaching rotary valves to the edges of cylinders, the distance between inlet and outlet are widened, to easily prevent a mixed air from being exhausted without being used, particularly in the case a four-cycle gasoline engine and a six-cycle gasoline engine, if an overlap is large. Thereby the waste of fuel is reduced.