A synthetic aperture radar apparatus comprising: - a synthetic aperture radar sensor configured to emit chirp signals into space, each chirp signal having a frequency changing with time and a range chirp rate indicating a rate of change of the frequency being switched, and configured to receive reflected waves of the chirp signals which are reflected by a target to thereby output received signals of the reflected waves; and - a signal processor including an image reconstruction processing means that is configured to perform range compression on the received signals output by the synthetic aperture radar sensor, and configured to reconstruct a synthetic aperture radar image from the received signals subjected to the range compression, - wherein the signal processor is further configured to: perform a discrete Fourier transform in a range direction on the received signals output from the synthetic aperture radar sensor; multiply the received signals subjected to the discrete Fourier transform in the Fourier transform unit, by function values of a complex function which determines, from both the range chirp rate at an azimuth time and an azimuth angle in a transmission direction of the chirp signal at the azimuth time, an amount of compensation for a peak shift of a distance between the synthetic aperture radar sensor and the target, the peak shift occurring in the received signal subjected to the range compression performed by the image reconstruction processing means, due to a movement of the synthetic aperture radar sensor during a time period until the reflected waves of the chirp signals are received by the synthetic aperture radar sensor after the chirp signals have been emitted from the synthetic aperture radar sensor; and perform a discrete inverse Fourier transform in the range direction on the received signals obtained by the multiplication of the function value, and wherein the azimuth angle in the transmission direction of the chirp signal changes with the azimuth time. - a synthetic aperture radar sensor configured to emit chirp signals into space, each chirp signal having a frequency changing with time and a range chirp rate indicating a rate of change of the frequency being switched, and configured to receive reflected waves of the chirp signals which are reflected by a target to thereby output received signals of the reflected waves; and - a signal processor including an image reconstruction processing means that is configured to perform range compression on the received signals output by the synthetic aperture radar sensor, and configured to reconstruct a synthetic aperture radar image from the received signals subjected to the range compression, - wherein the signal processor is further configured to: perform a discrete Fourier transform in a range direction on the received signals output from the synthetic aperture radar sensor; multiply the received signals subjected to the discrete Fourier transform in the Fourier transform unit, by function values of a complex function which determines, from both the range chirp rate at an azimuth time and an azimuth angle in a transmission direction of the chirp signal at the azimuth time, an amount of compensation for a peak shift of a distance between the synthetic aperture radar sensor and the target, the peak shift occurring in the received signal subjected to the range compression performed by the image reconstruction processing means, due to a movement of the synthetic aperture radar sensor during a time period until the reflected waves of the chirp signals are received by the synthetic aperture radar sensor after the chirp signals have been emitted from the synthetic aperture radar sensor; and perform a discrete inverse Fourier transform in the range direction on the received signals obtained by the multiplication of the function value, and wherein the azimuth angle in the transmission direction of the chirp signal changes with the azimuth time. perform a discrete Fourier transform in a range direction on the received signals output from the synthetic aperture radar sensor; multiply the received signals subjected to the discrete Fourier transform in the Fourier transform unit, by function values of a complex function which determines, from both the range chirp rate at an azimuth time and an azimuth angle in a transmission direction of the chirp signal at the azimuth time, an amount of compensation for a peak shift of a distance between the synthetic aperture radar sensor and the target, the peak shift occurring in the received signal subjected to the range compression performed by the image reconstruction processing means, due to a movement of the synthetic aperture radar sensor during a time period until the reflected waves of the chirp signals are received by the synthetic aperture radar sensor after the chirp signals have been emitted from the synthetic aperture radar sensor; and perform a discrete inverse Fourier transform in the range direction on the received signals obtained by the multiplication of the function value, and wherein the azimuth angle in the transmission direction of the chirp signal changes with the azimuth time.