A gas analyzing apparatus comprises: a light source (34) emitting an infrared luminous flux; a sample cell (38) which is arranged such that a sample gas is introduced therein and the infrared luminous flux emitted from the light source (34) is transmitted therethrough; and detection means (10a) which contains an absorber and is arranged such that the infrared luminous flux transmitted through the sample cell (38) passes through the absorber.
An increase in pressure, according to the temperature within an absorber container raised upon absorption of the infrared luminous flux by the absorber, is optically detected so as to measure, based on the increase in pressure, a concentration of an ingredient to be measured in the sample gas; wherein, as the absorber contained in the detection means (10a), a gas having an ingredient identical to the ingredient to be measured is used; particularly high sensitivity being obtainable by the provision of at least two detection means (10a,10b) containing gases having respective ingredients identical to different ingredients to be measured in the sample gas.