A motor, to which a rotary joint supporting structure for supporting a rotary joint is attached, turns a spindle. The motor includes a motor housing, a rotary shaft having a hollow shape and penetrating through the motor housing in the axial direction of the spindle, a flinger integrally attached to the rotary shaft outside the motor housing and disposed on the side to which the rotary joint supporting structure is attached, and a peripheral wall provided on the motor housing and projecting in the axial direction of the spindle so as to surround the periphery of the flinger. A plurality of cutouts are formed in the peripheral wall so as to establish communication between the interior and the exterior of the peripheral wall.