PURPOSE: To maintain an excess length part substantially in a ring state by a desired large radius of curvature irrespective of an extent of the length and to eliminate a fear of limiting a pattern forming region in an excess length processing structure for an optical fiber to be wired on a mounting surface of a printed circuit board.

CONSTITUTION: A frame member 30 to be fixed to a mounting surface of a printed circuit board 1 having a placing area of an optical module 5, a cover 35 detachably covering an opening of the member 30, and an optical fiber 10 connected at one end to the module 5 and mounted at the other with an optical connector 12 are mounted on the sidewall of the member 30. An outside optical connector 16 mounted at an end of an outer wiring optical fiber 15 is provided outside the member 30, and an adapter 20 in which the connector 12 is plugged is provided inside the member 30. An excess length of the fiber 10 is contained in a ring state in the member 30.