The present invention is a nitride compound semiconductor laser, in which a cleaved end face is flat, and a breakdown of a laser end face induced during an operation can be suppressed, which consequently enables a life to be prolonged. A ratchet gear is contained in the first structure of a shape suitable to be slidably mated and loosely locked thereunto the second structure which contains a means for torquing introduction and implementation by a drive tool. The diode driver receives bias and modulation currents to control a laser diode for generating light signals.