PURPOSE: To detect safely human body, etc., with high sensitivity by detecting the magnetism state of a magnetic body through an SQUID fluxmeter while passing the detected body through an uniform magnetic field established by a magnetizing device.

CONSTITUTION: When the detected body 5, e.g. man passes through the uniform magnetic field produced by a magnetizing coil 1 while a moving head 4 moves as shown by an arrow a, the magnetic body in the detected body 5 is magnetized. The SQUID fluxmeter 6 uses a differential type pickup coil 7, so the uniform magnetic field is canceled and not detected, and only magnetic flux variation due to the magnetized magnetic body is detected. The detection output is amplified by an RF amplifier 8 and the output generated by an SQUID controller 9 is recorded on a recorder 10.