Provided is a rotary blade engine including: an outer cylinder; an inner cylinder; an output shaft; an operation chamber; and a blade, wherein the inner cylinder is provided inside the outer cylinder, and rotates about a second center axis as a center of rotation, the second center axis being provided at a position eccentric from a first center axis of an inner peripheral surface of the outer cylinder; the output shaft is inserted into the inner cylinder, and rotates about the first center axis as a center of rotation; the operation chamber is formed between the outer cylinder and the inner cylinder; and the blade is fixed to the output shaft, rotates together with the output shaft, and defines the operation chamber by floatably penetrating the inner cylinder from an inside of the inner cylinder and slidably contacting the inner peripheral surface of the outer cylinder.