Abstract: A side pressure type rotary engine of a simple construction is formed by a cylinder having a suction port and an exhaust port in predetermined portions thereof, a main shaft passed through the cylinder, a rotor provided at both sides of flat surface portions thereof with a pair of working chamber-forming recesses and adapted to be rotated unitarily with the main shaft, a fixed blocking element, an active block, a suction and exhaust blocking element and an expansion blocking element which are movable in the axial direction of the main shaft, and a cylindrical cam and rocker arms which constitute a driving mechanism for moving the active block, suction and exhaust blocking element and expansion blocking element. The rotor is rotated to move the active block, suction and exhaust blocking element and expansion blocking element at predetermined timings and strokes, whereby suction, compression, expansion and exhaust strokes are carried out.