To suppress a leak amount of explosion combustion gas by making a cylinder in a rotary engine and rotors contact with each other, and to improve the fuel economy of the engine.

The two rotors independently rotating in a cylindrical cylinder are assembled, and the inside of the cylinder is divided. Each rotor and a drive shaft are connected by elliptical gears. At this point, the elliptical gears are installed at the drive shaft so that one of the gears forms a long diameter and the other forms a short diameter with respect to the same directions. By constantly rotating the drive shaft, the drive shaft rotates while repeating an increase and decrease of a capacity of each chamber. When pressure is generated by ignition explosion at a time point of the minimum capacity, torque is transmitted to the drive shaft in a positive direction and a reverse direction from each rotor, and motive power is obtained by rotation generated by the difference of the torque. By forming an intake port, an ignition device and an exhaust port at a position in which the capacity is minimum, a series of cycles of an intake stroke, a compression stroke, an explosion stroke and an exhaust stroke of the rotary engine can be obtained.