Disclosed is an electro-magnetic tomography including: a modulator configured to modulate a generated transmit reference signal using a pseudo-noise signal; a transmitter configured to transmit the signal modulated by the modulator; a receiver configured to receive a signal transmitted from a transmitter; an amplitude detector configured to compare an amplitude magnitude between the signal received by the receiver and the transmit reference signal to measure a received amplitude; and a demodulator configured to demodulate the signal received by the receiver using the pseudo-noise signal to generate a cyclic signal, compare a phase between the transmit reference signal and the cyclic signal to measure the phase of the cyclic signal, and determine the phase of the received signal based on the phase of the measured cyclic signal.