PURPOSE: To obtain a rotary piston engine of small vibration by providing the first/second rotors, rotatably supported to a rotor shaft, in the first/second rotor chambers, vertically movable shield units in each rotor chamber, intake air hole in the first rotor chamber, exhaust hole in the second rotor chamber, spark plug and a connection hole of both the rotor chambers.

CONSTITUTION: Rotors 2, 11 are placed in the first/second rotor chambers 1, 8 and rotatably supported to a rotor shaft 3 through connection disks 2a, 11a. The first/second shield units 6, 14 are vertically movably stored in opening parts respectively of the rotor chambers 1, 8, to form operating chambers 11, 12. An intake air hole 7 is provided behind the shield unit 6, a connection hole 9 having a check valve 10 is provided before the shield unit 14, and an exhaust hole 17 is provided in the rear. Mixture gas is sucked from a suction hole 7, compressed by the rotor 2, fed to the rotor chamber 8 and exploded between the shield unit 14 and the rotor 11. By this constitution, a rotary piston engine of high thermal efficiency is obtained with no vibration by eliminating an eccentric motion part.