PURPOSE: To provide a thin thermistor element having small heat capacity, excellent sensibility and large handling strength.

CONSTITUTION: An electrode is formed on a ceramic element assembly consisting of composite ceramics, in which there are semiconductor ceramics in the pores of an insulating ceramic porous body, in a thermistor element. The insulating ceramic porous body is impregnated with a solution containing a precursor forming semiconductor ceramics by baking and baked, and the electrode is formed onto the acquired composite ceramic sintered body. Accordingly, an infrared sensor having remarkable high sensibility can be manufactured easily.