PURPOSE: To revolve a rotor in a housing by carrying-out the suction of mixed gas, compression, explosion, and the discharge of combustion gas by the reciprocating movement of a vane incorporated into the rotor.

CONSTITUTION: A vane 3 incorporated into a rotor 1 performs the reciprocation movement inwardly and outwardly from the rotor 1, together with the revolution of the rotor 1 in a housing 6. In other words, the vane 3 is moved inwardly when mixed gas is inhaled in the vicinity of a suction port 7, and outwardly when the mixed gas is compressed, and the vane 3 is moved inwardly, increasing the turning-moment by receiving the thermal expansion force of the combustion gas, when explosion occurs in a combustion chamber 8, and the vane 3 moves outwardly when combustion gas is discharged in the vicinity of a discharge port 9. The reciprocating movement of the vane 3 in the elliptical movement of a planetary shaft part 5 around an anchor shaft 4. With such constitution, the rotor 1 revolves in the housing 6.