Movable end portions of cables and are fixed to a movable lead block, and fixed end portions of the cables are fixed to a fixed lead block. The movable lead block is mounted so as to be inserted into a cylindrical portion of a rotary body in a direction along a rotation center line, and the fixed lead block is mounted so as to be inserted into a lead block attachment portion of a lower housing in the direction along the rotation center line. The movable end portions and the fixed end portions of the cables are positioned at the same heights as those of the cables in a wiring space.