PURPOSE: To prevent the deviation of an optical axis and to eliminate need for fixing a collimator lens and a semiconductor laser on an adjustment device when they are fixed after a distance between them is adjusted.

CONSTITUTION: A collimator lens barrel 34 is inserted in the fit hole 36 of a holder 30 made extending over a coupling part 33 from a fit part 32 and temporality fixed. A deformation part 38 is formed so as to be extended from the coupling part 33 side along in the axial direction of the fit part 32 in cantilever. Then, the projecting part 38A of the deformation part 38 is made to project from the outside diameter of the lens barrel 34. When the lens barrel 34 is inserted, the deformation part is elastically deformed. By the reaction thereof, the lens barrel 34 is pressed to the side faced to the deformation part 38 through the optical axis B. Therefore, even when the lens barrel 34 is slid according as the distance is adjusted, the positional deviation is not caused with respect to the optical axis B.