An optical fiber laser module is provided with an optical fiber (2) for diffusing light, and a laser module housing (1) connected to the optical fiber. The laser module housing is provided with a laser light source (11) that outputs laser light to the optical fiber, and a light detector (14) that detects laser light that has been wave-guided through the full length of the optical fiber. The optical fiber is provided with: a light incident part (3a) provided inside the laser module housing, laser light from the laser light source being incident on the light incident part; and a terminal part (3) on which is formed a reflective film (4) that reflects the laser light that was incident on the light incident part and was wave-guided through the full length of the optical fiber so as to return the laser light to the light incident part.