PURPOSE: To identify simply a person, etc. by storing a value of a resonance frequency when a specified material is inserted into a coil of an RLC resonance circuit.

CONSTITUTION: If a finger 7 is inserted into a magnetic field of a coil 9 in the RLC resonance circuit 8, an (R) component is applied eqivalently in series to (L), and the resonance frequency is varied. The resonance frequency obtained by inserting the finger 7 of a specified person is measured by a frequency indicator 13, and is stored in a memory circuit 4 through an AD converter 2. Next, in case of identifying the person, a changeover switch 6 is connected to the (b) side, the finger 7 of the person is inserted into a coil 9, the resonance frequency at the time is compared with the value stored in the circuit 4 by an identification processing circuit 5. Thereby, whether the person is identical with a registered person or not is judged.