PURPOSE: To reduce the change in sensitivity due to the change in the ambient temperature in operation, to reduce the inductive noise, and to increase the linearity, by respectively providing the thermister for infrared ray detection and ambient temperature correction on one isolating board.

CONSTITUTION: On the common insulation wafer 11, the ambient temperature correction thermister 8 and the infrared ray detection thermister 9 are provided, and the electrodes 12 to 14 are provided at the both ends of each thermister. Accordingly, the resistance change in ambient temperature is the same for the both thermistors, and the sensitive characteristics to infrared ray input energy can be increased by processing the difference signal of the both. Further, the linearity of the both elements can be increased with parallel connection of the resistors 15 and 16 to the elements 8 and 9 respectively.