In addition to the optically passive alignment between the optical fiber and the semiconductor device using a V-groove provided on a substrate made of silicon single crystal, the active alignment therebetween may be carried out for enhancing the optical coupling efficiency. According to the present invention, the optical module provides a coupling member including a center waveguide and a sheath member covering the center waveguide. The outer shape of the sheath member is an elliptic so that the center position of the center waveguide may move as the coupling member rotates in the V-groove such that the outer surface thereof touches two sides of the V-groove. Accordingly, the optical coupling efficiency with the semiconductor device may be varied. The ellipticity of the elliptic outer shape is preferably greater than unity and not greater than 2, and the bottom angle of the V-groove is preferably not smaller than 60 and not greater than 120, in particular, the angle is preferably a right angle in substance.