Patent ID: 8085404

Claim:
A gas analyzing method, comprising the steps of: demultiplexing laser light by a demultiplexer into measurement laser light and reference laser light; letting the measurement laser light pass through gas to be received by a photoreceiver; finding an absorption spectrum absorbed by a gas component in the gas based on a light intensity of the received measurement laser light and a light intensity of the reference laser light; and analyzing the absorption spectrum to measure a concentration of the gas component, wherein the measurement laser light is applied to the gas through an optical attenuator, and control is conducted by the optical attenuator so that the light intensity of the measurement laser light that has actually passed through the gas has a predetermined relationship with the light intensity of the reference laser light, wherein a signal of the light intensity of the measurement laser light that has actually passed through the gas is not input to an analysis unit that analyzes the absorption spectrum, so as to reduce an amount of data to be input to the analysis unit.