PURPOSE: To reduce the force for turning-driving and stopping of a carrier with a simple structure by rotatably supporting a turning motion driving small gear with one of a weight supporting stand and a turning stand, and fixing an internal gear type turning-driving large gear to be engaged with the small gear to the other one.

CONSTITUTION: In a turning device 6, an internal gear type large gear 64d is used, and since a small gear 64c and the large gear 64d are engaged with each other more far from the center of the small gear 64c against the rotary shaft core of a turning stand 63 to drive or stop the turning of a carrier 7, the force to be transmitted from the small gear 64c to the large gear 64d is reduced. As a result, the power required for turning the carrier 7 is reduced, and a turning motion driving device 64 is made compact to lower a cost, and while the driving energy can be saved. Besides, the braking force of a motor 64a for stopping the carrier 7 can be reduced, and the motor 64a can be made more compact to lower the cost more, ad turning of the carrier 7 can be stopped securely to control the turning position accurately.