According to an embodiment, a control circuit of an equalizer configured to set a first amount to a linear equalizer, determine a second amount optimizing a non-linear equalizer with respect to a first signal generated by the linear equalizer to which the first amount is set, set the second amount to the non-linear equalizer, update an amount from the first amount to a third amount smaller than the first amount based on a magnitude of the first amount, set the third amount to the linear equalizer, determine a fourth amount optimizing the non-linear equalizer with respect to a second signal generated by the linear equalizer to which the third amount is set, and update an amount from the second amount to the fourth amount.