PURPOSE: To detect metal and nonmetal with high precision by providing an induction type detector including an exciting and a receiving coil and a radio wave type detector successively, providing a compensating coil in the exciting coil of the induction type detector, and arranging the radio wave detector in the compensating coil.

CONSTITUTION: The compensating coil 4 is connected to the exciting coil 1 in series, and both coils 1 and 4 are connected to an oscillator 6. When the oscillator 6 is driven, an exciting current flows through the coil 1 to produces a magnetic field at the circumference, and it is received by receiving coils 2 and 3. If there is a metallic body, and eddy current magnetic field is produced to vary the magnetic field detected by the coils 2 and 3. This variation is amplified by an AC amplifier 7, whose output is rectified synchronously by synchronous rectifying circuits 9 and 10 with a 0-phase and a π-phase signal from a phase adjusting circuit 8 and amplified by DC amplifiers 11 and 12. Consequently, a detection signal of magnetic metal appears at an output terminal and a signal of nonmagnetic metal appears at an output terminal 14, so that wide-range detection is performed.