Laser working machine

Machine laser machining (11) with laser radiation, preferably a CO2 laser, provided for machining a piece of material with a measuring cell (2; 12) in which can enter a gas machine of machining laser to analyze, especially a feed gas laser and / or machine laser machining (11) or cutting gas and / or a working gas, characterized in that it is equipped with a system (7) for decoupling a diagnostic radiation (5; 14) from the laser radiation and an acoustic detector to record the called photoacoustic effect that occurs in the measuring cell (2; 12) after absorption of radiation diagnosis (5; 14).