PURPOSE: To realize the optical transmission even for a machine including a rotary part, by supporting a sleeve which rotates along with the 1st optical fiber at a fixed part to be connected to the 2nd optical fiber so as to avoid the change of optical axes of both optical fibers.

CONSTITUTION: A sleeve 14 is provided around the edge part of an optical fiber 11 of the rotating side so that a coincidence is obtained for the optical axes between the optical fiber 11 connected to a rotary part and an optical fiber 12 to be connected to a fixed part. The edge part of the fiber 12 of the fixed side is supported by a holder 15, and a projected part 17 provided at the intermediate part of the sleeve 14 is accepted at a chin part 18 of the holder 15 and supported by a holding parts 16. In such constituion, both the sleeve 14 and the fiber 11 are rotated around the optical axis by the rotation of the rotary part. Even in such case, the optical axis of the fiber 11 has no change substantially. Thus the transmission loss between the fibers 11 and 12 which are held opposite to each other and with a prescribed space can be neglected even in the rotating state.