Abstract: A magnetic detector includes a magnetizer generating a magnetic field; a first magnetic sensor for detecting a leakage flux resulting from a magnetically defective portion of an object moving in and relative to the magnetic field; a low-pass filter for extracting a low-frequency signal component contained in the signal output by the magnetic sensor, the low-frequency signal component being indicative of a floating flux which crosses the magnetic sensor and is a result of the object moving through the magnetic field; an amplifier for amplifying the extracted low-frequency signal component; a compensating coil excited by the amplified low-frequency signal component output by the amplifier, for generating a magnetic flux which cancels out the floating flux crossing the magnetic sensor; a high-pass filter for extracting a signal resulting from the magnetically defective portion and contained in the signal that is output by the first magnetic sensor; an output amplifier for amplifying a signal output by the high-p