PURPOSE: To reduce the energy toss and increase the output by providing a through hole in the radial direction of rod shape which penetrates an air intake/ exhaust valve of a reciprocal internal combustion engine, and intaking or exhausting the air-fuel mixture or the exhaust gas by rotating the hole.

CONSTITUTION: In a rotary air intake/exhaust valve, an air intake valve l and an exhaust valve 2 are of rod shape. The respective rod-shaped valves are radially provided with holes 3,4 where the air-fuel mixture or the exhaust gas flows therein or is exhausted therefrom. In the four-cycle gasoline engine, the rotary air intake/exhaust valve is driven after obtaining 1/4 speed reduction from the crank shaft 8. In this rotary air intake/exhaust valve, the rotation of the crank shaft 8 is reduced to 1/4 by a roller chain or a timing belt. In the air intake stroke, the hole 3 is opened to allow the fuel-air mixture to flow into the cylinder. In the exhaust stroke, the hole 4 is opened to exhaust the exhaust gas. Thus, the energy loss is reduced and the output is increased.