Provided is an optical semiconductor module in which the shift upon lens fixation is effectively corrected. Between a semiconductor laser (101) and a semiconductor modulator (105) are arranged a first lens (102), a second lens (103), and a third lens (104). The first lens (102) and the second lens (103) constitute a collimate lens optical system. The first lens (102) makes the lights emitted fromthe semiconductor laser (101) to be parallel lights. The second lens (103) converges the parallel lights which are coupled to the semiconductor modulator (105). The third lens (104) has a long focal distance as compared to the first and the second lens (102, 103). The positions of the first and the second lens (102, 103) are adjusted and fixed. Then, the position of the third lens (104) is adjusted and fixed. This effectively corrects the shift upon lens fixation.