A rotating mechanism comprises a biasing means (4) and a damper means. When a movable body (2) is changed over from the first position to the second position and from the second position to the first position of a body (1), the rotating mechanism rotates the movable body (2) against the biasing force of the biasing means midway during the changeover operation, rotates the movable body (2) by the biasing force of the biasing means (4) after the midway, and brakes the movable body (2) by the damper means in a predetermined interval in which the movable body is rotated by the biasing force. The rotating mechanism is characterized in that the movable body (2) comprises an arm (21) rotated integrally, and the damper means is a piston damper (3) which is rotatably supported on the body (1), connected directly or indirectly to the arm (21), and so installed that the extending/retracting direction of the movable body (2) can be changed over during the changeover operation. Consequently, the usability and the quality of the rotating mechanism can be improved by optimally braking the rotating mechanism by the damper means.