To easily provide a coin identifying sensor in which an error due to a fluctuation in environmental temperature is decreased.

An exciting coil 3 is driven with constant currents supplied from a constant current driving circuit 12, and the temperature fluctuation of a coin material quality identification signal is put in a status where the temperature fluctuation based on the coil resistance value DCR of the exciting coil 3 is removed, and made to correspond to the fluctuation based on the temperature fluctuation of a permeability μ of a sensor core SC. The temperature characteristics of the permeability μ of the sensor core SC or the temperature characteristics of an applied voltage from a constant current driving circuit 12d to the exciting coil 3 are previously estimated, and the estimated temperature is easily and highly precisely corrected by a temperature correction means installed in a CPU 14.