ROTARY OPERATING UNIT

PROBLEM TO BE SOLVED: To obtain a rotary operating unit having a self-aligning function for correcting unbalance (shift of the center of gravity) of a rotator, e.g., a disc table, in which self-alignment is carried out quickly and surely. SOLUTION: An annular magnet 24 and a pair of magnetic yokes 25 sandwiching the magnet 24 are arranged in a chucking pulley being rotated by a spindle motor along with a magnetic disc. A plurality of balancer balls 13 are contained in the magnetic yokes 25. At the time of stopping or starting rotation of the chucking pulley, the balancer balls 13 are attracted to the magnetic yokes 25. In high speed rotation, the balancer balls 13 roll in the circumferential direction along the inner circumferential edge of the magnetic yokes 25 to perform self-alignment.