A semiconductor laser module includes a polarization direction transforming part which transforms polarization directions of first and second laser beams such that they are orthogonal to each other even if a polarization dependent optical isolator is utilized in the semiconductor laser module. The configuration allows the two laser beams to propagate through the birefringence element to the output port without each splitting into an ordinary ray and an extraordinary ray on entering the birefringence element, and therefore free from decrease of optical power reaching the output port. Thus, high power semiconductor laser modules can be provided.