To provide an adaptive equalizer in which convergence of a tap coefficient is improved while preventing degradation of follow-up characteristic of a PLL circuit.

The equalizer is made to be such primary coupling that group delay is a 0 part yei and a non-0 part y0i, group delay of the 0 part yei is used for calculation of a phase error of the PLL circuit. By constituting the device as the above, since a group delay characteristic of a filter realizing yei does not depend on a coefficient {kei} but is always 0, even if convergence of the coefficient {kei} is improved, influence for a follow-up characteristic of the PLL circuit is small. Also, as y0i is not used for calculation of a phase error of the PLL circuit, even if convergence of the coefficient {k0i} is improved, follow-up characteristic of the PLL circuit is not degraded.