A rotating device comprising: - at least one ring that is configured to rotate in a circumference direction, the at least one ring including no hub for housing a motor, inside the at least one ring; - at least one motor that is configured to generate power for rotating the at least one ring; and - a power transmission mechanism that is configured to transmit the power to the at least one ring, wherein the at least one ring includes: - a first ring rotating around a first central axis, the first ring being disposed at a first position; and - a second ring rotating around a second central axis, the second ring being disposed at a second position different from the first position, the first central axis and the second central axis lying on the same straight line, wherein a first diameter of the first ring is different from a second diameter of the second ring, the first position is different from the second position in a rotating radial direction, and the power transmission mechanism is configured to transmit torque, output from the at least one motor, to each of the first ring and the second ring so that, by the torque, the first ring and the second ring rotate in directions opposite to each other or in a same direction at rotating speeds different from each other, characterised in that the first ring is disposed inside the second ring, and the at least one motor is disposed in an annular space formed between the first ring and the second ring. - at least one ring that is configured to rotate in a circumference direction, the at least one ring including no hub for housing a motor, inside the at least one ring; - at least one motor that is configured to generate power for rotating the at least one ring; and - a power transmission mechanism that is configured to transmit the power to the at least one ring, wherein the at least one ring includes: - a first ring rotating around a first central axis, the first ring being disposed at a first position; and - a second ring rotating around a second central axis, the second ring being disposed at a second position different from the first position, the first central axis and the second central axis lying on the same straight line, - a first ring rotating around a first central axis, the first ring being disposed at a first position; and - a second ring rotating around a second central axis, the second ring being disposed at a second position different from the first position, the first central axis and the second central axis lying on the same straight line, wherein a first diameter of the first ring is different from a second diameter of the second ring, the first position is different from the second position in a rotating radial direction, and the power transmission mechanism is configured to transmit torque, output from the at least one motor, to each of the first ring and the second ring so that, by the torque, the first ring and the second ring rotate in directions opposite to each other or in a same direction at rotating speeds different from each other, characterised in that the first ring is disposed inside the second ring, and the at least one motor is disposed in an annular space formed between the first ring and the second ring. a first diameter of the first ring is different from a second diameter of the second ring, the first position is different from the second position in a rotating radial direction, and the power transmission mechanism is configured to transmit torque, output from the at least one motor, to each of the first ring and the second ring so that, by the torque, the first ring and the second ring rotate in directions opposite to each other or in a same direction at rotating speeds different from each other, characterised in that the first ring is disposed inside the second ring, and the at least one motor is disposed in an annular space formed between the first ring and the second ring.