Abstract: A detector for an infrared gas analyzer is formed of first and second light receiving rooms filled with gas to be analyzed, a gas passage communicating between the first and second light receiving rooms, and a heat-sensitive resistance element disposed perpendicularly to the gas passage. The heat-sensitive resistance element includes at least one heat insulator having an opening at a center thereof, a pair of heat-wire elements disposed on the heat insulator to face against each other with a predetermined space therebetween, and a heating device. Each heat-wire element has a plurality of elongated elements disposed parallel to each other in the opening of the heat insulator, and connecting portions for connecting ends of the elongated elements for serially connecting the elongated elements. The heating device is formed on the heat insulator around the opening to equalize temperature in a space surrounded by the heat-wire elements in the opening. Accordingly, the analyzer can be operated stably.