PURPOSE: To produce an inexpensive and sure attendance confirming device by confirming the attendance by the oscillation state of an oscillating system.

CONSTITUTION: The coil of a first coil group order 1 is selected by a first scanner 10 and is connected to the input side of a voltage amplifier 3, and a coil of a second coil group order 1 is selected by a second scanner 20 and is connected to the output side of a current amplifier 4. Then, the coil of the first coil group order 1 (first oscillating element), the voltage amplifier 3, the current amplifier 4 (third oscillating element), and the coil of an ID card carried by a student sitting in a position (fourth oscillating element) constitute the oscillating system, and the oscillating system oscillates with its natural frequency. It is detected by a processor 5 that this oscillating system has a prescribed or higher level. As the result, the processor 5 enters turning-on of this position in an incorporated first memory.