To easily evade a radio interference fault, even though plural similar devices to a heat ray sensor device are placed nearby by using the infrared signals for the wireless communication between a heat ray sensor slave unit and a heat ray sensor master unit.

A heat ray sensor device includes a heat ray sensor slave unit 1 and a heat ray sensor master unit 2. A heat ray sensor part 10 of the unit 1 consists of current collection elements to detect the change of the heat ray received from a detection area, i.e., a lens visual field range and output the voltage, corresponding to the changed amount of the heat ray. A comparison part 12 has a preset reference voltage and always monitors whether the voltage outputted from an amplification part 11 exceeds the reference voltage. When the voltage exceeds the reference voltage, the part 12 decides the occurrence of an event on an object to have been detected, that is, e.g. that a person has intruded the detection area and then outputs a detecting object event occurrence signal to a signal processing part 13. The part 13 transmits an infrared signal W of a prescribed transmission protocol.