This invention makes it possible to measure a concentration of a gas component having the adsorption even thought the concentration is low, and to improve a response speed of the measurement of the concentration, and comprises a body 2 that has an introduction port 2P to introduce a sample gas into a measurement cell 21, a laser light irradiation part 22 that irradiates the laser light L1 on the measurement cell 21, a heating pipe 4 that applies heat to the sample gas introduced into the introduction port 2P, a flow rate limit part 32 that makes the sample gas at a negative pressure and that introduces the negative-pressurized heated sample gas into the body 2, and a negative pressure pump 24 that keeps inside of the measurement cell 21 and a flow channel from a downstream side of the flow rate limit part 32 to the measurement cell 21 at the negative pressure.