PURPOSE: To shorten a time required for a humidity detecting element which has been heated for removing a sticking contaminant by burning off to be cooled down to a temperature at which it can detect humidity again.

CONSTITUTION: A humidity detecting element 11 fitted with a heater 20 is suspended between support wires 51 and 52 provided upright on a pedestal 60, through the intermediary of heating wires 41 and 42. Signal wires 43 and 44 are connected to support wires 53 and 54, while a protector 80 is put on the pedestal 60 and further a filter 90 for filtering a contaminant in gas is put on the protector 80. Since the humidity detecting element 11 can radiate heat from the whole surface, according to this constitution, a time for cooling can be shortened.