PURPOSE: To extremely shorten time for training by setting the initial tap coefficient of the adaptive equalizer(AE) corresponding to the reverse characteristic of a fixed part without any time fluctuation in the frequency characteristic of a transmission line.

CONSTITUTION: The initial tap coefficient to form the reverse characteristic of the fixed part in the frequency characteristic of the transmission line stored in a memory 1 for initial tap coefficient is loaded to an AE 2. Next, an already known pseudo random signal to be transmitted from the transmission side is demodulated by a demodulator 5 so as to remove distortion generated by the fixed frequency characteristic by the AE 2. Afterwards, a decider 3 calculates error caused by signal distortion generated from an unknown frequency characteristic, and based on the error, a tap coefficient updating device 4 executes operation for updating the tap coefficient so as to update the tap coefficient of the AE 2. Then, the similar processing is repeated only for time set in advance, training is finished and continuously, data is transmitted.