In an apparatus wherein an infrared sensor is incorporated opposite to an opening formed at a predetermined position of a housing, a distance keeping member for keeping a constant distance from a temperature measuring portion is further mounted on another predetermined position of the housing, and an output signal from the infrared sensor responding to the infrared rays from the temperature measuring portion is supplied to a temperature measuring circuit whose operational state is selected by a temperature measurement control switch, and the temperature of the temperature measuring portion is displayed on a display unit which is driven by the output signal from the temperature measuring circuit.