PURPOSE: To permit high efficiency transmission of optical signals even if the axis of a steering shaft becomes eccentric to a car body, by connecting a lower side housing of a slip ring to be regulated with respect to only rotational movement relative to the car body side.

CONSTITUTION: An engaging projection 34 projecting axially from the lower surface of the center portion of a lower side housing 23 is provided to fit properly loosely between two rotation regulating pieces 36, 37 projecting in parallel from the outer periphery of a ring 35 press fitted onto the end of a steering column tube 5. Thus, the rotational movement of the lower side housing 23 is regulated by the engaging projection 34 and the rotation regulating pieces 36, 37 and the axial movement of same is allowed along the rotation regulating pieces 36, 37.