For preventing an optical axis from shifting due to a heat cycle in a semiconductor laser module, or in a optical transmitter, the semiconductor laser module comprises, a semiconductor laser element, a frame for storing the semiconductor laser element therein, an optical fiber fixing portion being connected to the frame; and a flange being connected to the frame, and having a fixing portion for fixing the frame on a substrate, wherein the flange has a narrow width region between a fixing region, including a foxing portion with the substrate therein, and the frame, and the narrow width region is narrower than width of the fixing region.