PURPOSE: To perform control according to whether a man exists or not by supplying the outputs from IR sensors provided to face the reflecting surfaces in the same direction of plural condensing mirrors via a detector for the intruding direction of the object to be inspected to a counter and outputting the prescribed on or off signal with the output thereof.

CONSTITUTION: Pyroelectric type IR sensors 3, 3 are provided to face reflecting surfaces 2, 2 in the same direction of plural, for example, two condensing mirrors 1, 1 and the signals therefrom are supplied via amplifier circuits 4, 4 to a detector 5 for the intruding direction of the object to be inspected by which the intruding direction of the object 6 is discriminated and the prescribed signal is supplied to a counter 7 for the number of the object to be detected. The number of the objects 6 in every intruding direction is counted by the counters 7 and whether the person exists in or out of the detecting region or not is detected. When the counter judges, for example, that there are no persons in a room, an off signal is outputted via a controller 8 connected to the counter 7 and is supplied to an electrical apparatus for illuminating in the room, air conditioning, etc. The economization of electric power and the prevention of disasters are thus accomplished.