a delay unit for delaying a feedback signal obtained from the second signal;

a delay control unit for determining a delay quantity of said delay unit so that a timing difference being applied to a distortion compensation signal updating unit and between a reference signal obtained from the first signal and the feedback signal delayed by said delay unit is made small; and

a frequency adjusting unit for adjusting a frequency of carrying out a process that said delay control unit determines the delay quantity, wherein

said delay control unit limits the delay quantity within a limit value,

when the delay quantity exceeds a threshold and approaches the limit value, the frequency of carrying out the process that said delay control unit determines the delay quantity is made higher than that in the case where the delay quantity does not exceed the threshold,

the frequency adjusting unit comprises a timer,

the delay control unit determines the delay quantity when the timer is timed out,

a time-out period is shortened while the delay quantity exceeds the threshold and approaches the limit value, and

the time-out period is lengthened while the delay quantity returns within the threshold.