To provide a coefficient updating method for a time domain equalizer for a DMT(Discrete Multitone Modulation) system by which an optimum coefficient can be obtained even for a data period and a processing amount of coefficient updating can be relieved.

A coefficient of a TEQ(Time Domain Equalizer) 32 is updated from an output of the time domain equalizer (TEQ 32) in the DMT system. Since a transient of a SYNC symbol added with a cyclic prefix for a data period can be eliminated, even when the SYNC symbol is used, the coefficient of the TEQ can accurately be updated. Thus, since the coefficient of the TEQ is updated even during the data period, the coefficient of the TEQ 32 in response to the characteristic change can be updated even from a channel whose characteristic is changed. Moreover, since an output of an FFT (36) of a main path at a post-stage of the TEQ (32) is used, the processing quantity of the FFT in the coefficient correction can be reduced.