PURPOSE: To improve the sensitivity of detection and make buried metallic pipes accurately searchable by detecting the magnetic fields generated from the buried metallic pipes such as water supply pipes, telephone cables or the like by means of a detecting coil constituted by the combination of a vertical detecting coil and a horizontal detecting coil, and combining the output waveforms of both vertical and horizontal detecting coils.

CONSTITUTION: A detecting coil 1 is constituted of a vertical detecting coil 2 having a vertical coil axis and a horizontal detecting coil 3 having a horizontal coil axis. The coil 2 is connected via an amplifier 4 and a filter 5 to one input terminal 6a of a differential amplifier and the coil 3 is similarly connected to the other input terminal 6b of the amplifier 6. Electric current is flowed to a buried metallic pipe A to generate a magnetic field. When the coils 2, 3 are moved, the output waveformIbottoming at the point right above the pipe A is obtained from the coil 2 and the output waveform II peaking at the point right above the pipe A is obtained from the coil 3. These are combined with the amplifier 6 and the output waveform II of a sharp shape peaking at the point right above the pipe A is formed, and is displayed in a display device 10.