PURPOSE: To shorten the convergence time of the whole training by decreasing the number N of taps in the beginning of the training and adjusting tap coefficient values, and increasing the number N of taps in the middle of the training.

CONSTITUTION: The switching circuit 10 of a transversal filter is opened in the beginning of the training to provide feedback to only tape coefficients CM-k∼ CM+k. Further, the number of taps is small, so a tap number new coefficient value (g) is set to a large value g1 (g1>g2) and a multiplier 8 multiplies an error quantity by it (g2: specific value (g) used in data mode after training). A tap adjustment is made through this constitution and the switching circuit 10 is closed when the error quantity outputted from an adder 7 becomes smaller than a specific reference value, thereby providing feedback to all tap coefficients 3. At this same time, the switching circuit 9 switches the coefficient value from g1 to g2 and the tap coefficient 3 is adjusted.