Power amplifier circuit incorporating a negative feedback circuit for a transmitter and phase control method therefor. An I-component test signal and an I-component baseband feedback signal are added for generating an I-component summing signal. A Q-component test signal and a Q-component baseband feedback signal are added for generating a Q-component summing signal. A carrier is orthogonally modulated with the I- and Q-component summing signals. A part of the modulated signal is orthogonally demodulated with the carrier, whereby I-component baseband feedback signal and Q-component baseband feedback signal are outputted. Phase of the carrier is changed in accordance with a phase control signal for holding the phase of the carrier at a time when the detected state of one of the i- and Q-component summing signals as selected meets predetermined condition.