PURPOSE: To provide a large out,put rotary engine capable of providing torque and output in proportion to a radius of a rotor.

CONSTITUTION: A circular cylinder 2 is provided in a rotor housing and a roughly fan type partition plate chamber 7 is provided on the outer periphery of the circular cylinder 2 with a bulkhead 46 between them. Additionally, a cylinder 9 for pressure balance and a link device chamber 8 are provided adjoining to the partition plate chamber 7. An eccentric circular rotor 3 is stored in the cylinder 2. A circular arc partition plate 4 installed on the head end of a partition plate arm 13 is stored in the partition plate chamber 7, and the head end of the partition plate 4 partitions the cylinder 2 ajoining to a surface of the rotor 3. The partition plate 4 is controlled by a lever crank mechanism provided out of the housing. A complementary curved surface wall 5 to complement a clearance of the cylinder 2 is controlled by a link mechanism of the link device chamber 8.