PROBLEM TO BE SOLVED: To improve the efficiency of electromagnetic probing.
SOLUTION: A method has a movable transmission antenna 10 that is arranged at a specific location on the ground and transmits an electromagnetic wave with a specific frequency while being electrically connected to a transmitter 11 and a reception antenna 20 that is electrically connected to a receiver 21 and receives electromagnetic waves being transmitted from the transmission antenna 10. The reception antenna 20 is constituted of 2-constituent detection antenna 22 and 23 for detecting the orthogonal two constituents of the synthetic magnetic field of primary and secondary magnetic fields. The receiver 21 measures detected two constituents and analyzes specific resistance p1 and p2 in vertical direction in underground from the magnetic field strength ratio and phase difference between the orthogonal two constituents of the synthetic magnetic field and a distance r between the transmission/reception antennas 10 and 20 and the frequency of the transmitted electromagnetic wave. On measurement, the transmitters/receivers 11 and 21 are moved along a line to be measured.