A negative feedback amplifier for a transmitter, in which a vector corrector outputs the corrected signals, an adder adds the feedback signals of the in-phase component and the quadrature component to the in-phase component and the quadrature component of the output of the vector corrector, respectively, a modulator performs a quadrature modulation with respect to the in-phase component and the quadrature component of the outputs from the adder, a power amplifier amplifies the output of the modulator, a demodulator performs a quadrature demodulation to a part of the output of the power amplifier and outputs the feedback signals of the in-phase component and the quadrature component, and the vector corrector performs a correcting operation of canceling an error of at least one of the phases and the amplitudes of the in-phase component and the quadrature component occurring in the demodulator.