An amplifier circuit, comprising: a quadrature modulator configured to quadrature-modulate an IQ baseband signal; an amplifier arranged to amplify the quadrature-modulated signal; a distortion compensation section configured to compensate for distortion to be caused in the amplifier based on first compensation coefficients; a quadrature modulation error compensation section configured to compensate the IQ baseband signal outputted from the distortion compensation section for a quadrature modulation error; an updating section configured to update second compensation coefficients that are used for compensation in the quadrature modulation error compensation section; an error estimation section configured to estimate an error for updating the second compensation coefficients, based on the IQ baseband signal before being compensated by the distortion compensation section, and an IQ baseband signal obtained by quadrature demodulation of the output of the amplifier, the updating section being further configured to update the second compensation coefficients based on the error for updating the second compensation coefficients; characterised by, a prediction section configured to calculate a prediction value of the output of the amplifier after updating of the second compensation coefficients, using (a) the error for updating the compensation coefficients and (b) an IQ baseband signal obtained by quadrature demodulation of the output of the amplifier before updating of the second compensation coefficients based on the error for updating the compensation coefficients; and wherein the distortion compensation section is further configured to calculate the first compensation coefficient based on the prediction value. a quadrature modulator configured to quadrature-modulate an IQ baseband signal; an amplifier arranged to amplify the quadrature-modulated signal; a distortion compensation section configured to compensate for distortion to be caused in the amplifier based on first compensation coefficients; a quadrature modulation error compensation section configured to compensate the IQ baseband signal outputted from the distortion compensation section for a quadrature modulation error; an updating section configured to update second compensation coefficients that are used for compensation in the quadrature modulation error compensation section; an error estimation section configured to estimate an error for updating the second compensation coefficients, based on the IQ baseband signal before being compensated by the distortion compensation section, and an IQ baseband signal obtained by quadrature demodulation of the output of the amplifier, the updating section being further configured to update the second compensation coefficients based on the error for updating the second compensation coefficients; characterised by, a prediction section configured to calculate a prediction value of the output of the amplifier after updating of the second compensation coefficients, using (a) the error for updating the compensation coefficients and (b) an IQ baseband signal obtained by quadrature demodulation of the output of the amplifier before updating of the second compensation coefficients based on the error for updating the compensation coefficients; and wherein the distortion compensation section is further configured to calculate the first compensation coefficient based on the prediction value.