PURPOSE: To improve the data transmission efficiency by providing a delay circuit and a tap coefficient initial value estimate section, using a training series section in a received signal to set a tap coefficient of an equalizing section to the initial value suitable for the state of a line.

CONSTITUTION: Delay circuits 10-15 retarding a received signal for a prescribed quantity and inputting the result to an equalizing section and a tap coefficient initial value estimate section 80 using a data of a training series section in a received signal so as to set the line fluctuation state thereby setting the initial value of the tap coefficient suitable therefor, are provided. The tap coefficient initial value estimate section 80 uses the data of the training series section in the received signal to set the tap coefficient of the equalizing section 500 to the initial value suited to the line state. Thus, the convering time is reduced and the length of the training series is reduced to realize the equalizer with high data transmission efficiency as a whole.