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 . <EOS>