PURPOSE: To transmit an optical signal without being interrupted by simple constitution by arranging optical fibers on plural concentrical circles formed around the rotary shaft of a 1st connector and fixing an optical system for condensing ring beams formed by the rotation of the 1st connector on an optical axis different from the rotary shaft of the 1st connector to a 2nd connector.

CONSTITUTION: When a bearing holder 18 constituting the 1st connector is rotated, light beams projected from the optical fibers 13, 14 are turned to concentrical circle-like ring beams 13a, 14a formed around the optical fiber 12. Respective light beams are turned to thin parallel beams by a rod lens 16. Since the light beams projected from the optical fiber 12 are radiated to a prism 34 rectangularly to the prism 34, the beams are straight projected, penetrated into a prism 33 and a transmission plate 24 and then made incident on a rod lens 16a fixed on a cap 27 constituting the 2nd connector. At that time, the slightly diffused parallel beams are also turned to a light beam 39 concentrated into an optical fiber end face part so as to be a point. On the other hand, light beams projected from the optical fibers 13, 14 are respectively turned to light beams 40, 41.