The present invention provides an apparatus for compensating a phase error of an RF band chirp signal by pre-distorting a base band chirp signal, including: a waveform generator to output the base band chirp signal; an RF modulator to output the RF band chirp signal by upconverting the base band chirp signal; an error calculation unit to calculate a phase error over time for a predetermined time by comparing the RF band chirp signal with an ideal chirp signal; a section division unit to divide the predetermined time into a plurality of time sections; a section combination unit to combine neighboring time sections based on the phase error; and a phase distortion unit to distort phase of the base band chirp signal in the combined time sections based on the phase error.