A laser module LM is provided with a quantum cascade laser 1, a tubular member 5, and an infrared detector 7. The tubular member 5 has a pair of opening ends 5a, 5b and is arranged so that one opening end 5a is opposed to a face 1b opposed to an emitting end face 1a of the quantum cascade laser 1. The infrared detector 7 is arranged so as to be opposed to the other opening end 5b of the tubular member 5. Light emitted from the face (rear end face) 1b opposed to the emitting end face (front end face) 1a of the quantum cascade laser 1 is guided inside the tubular member 5 to enter the infrared detector 7, and then is detected.