PURPOSE: To make sufficient adhesion or welding while reducing the sizes of constituent components of the welding structure for the lens holder to which an optical fiber is connected.

CONSTITUTION: This structure consists of a base 1 which has a lens holder insertion hole 1b, the cylindrical lens holder 2 which has a lens on its axis, a holder 3 for temporary fixation which is inserted into the lens holder 2 and temporarily fixed to the seat surface of the lens holder 2, and a welding ring 4 which is inserted into the temporarily fixed lens holder 2 and has its outer periphery permanently fixed to the seat surface of the base while covering the ring 3 for temporary fixation; and the ring 3 for temporary fixation and welding ring 4 are made nearly equal in external diameter and recessed and projection parts 3a and 4a which engage each other are provided between the ring 3 and welding ring 4 to permanently fix the outer periphery of the ring 3 for temporary fixation to the seat surface of the base 1.