Abstract: An internal combustion rotary engine has a housing which has a plurality of outer rotors and stators and bearings, the outer rotors having a plurality of curved channels on inner surfaces thereof and one of the stators having intake ports and a port for a spark plug; a shaft which is rotatably supported by the bearings and has a plurality of holes communicating with a center passage formed therein for flowing of a coolant; a central rotor being formed as a frustum and fixedly supported by the shaft and having a plurality of curved channels overlapping with the channels on the rotors at ends thereof, but in a reversed direction, and on a first conical surface at a middle portion thereof and a second conical surface with a larger slope than the first conical surface at a front portion thereof to define a combustion chamber.