A semiconductor laser module includes a semiconductor laser having an active region between a light-reflecting surface and a light-exit surface thereof, and an optical fiber optically coupled to the semiconductor laser and including an optical fiber diffraction grating. The optical fiber diffraction grating selectively reflects light within a predetermined wavelength band. The wavelength band has a width larger than a wavelength interval of a longitudinal mode of light resonating between the light-reflecting surface and the light-exit surface.