A frequency modulation radar apparatus for vehicle use can suppress the influence of noise to avoid incorrect estimation due to noise thereby to provide a beat frequency with high accuracy and at high speed without increasing the frequency resolution of the beat frequency that causes an increase in an observation time. The apparatus includes a frequency correction section that calculates a corrected frequency (f.sub.n+.delta.) by adding an amount of frequency correction (.delta.) to the frequency (f.sub.n) of a peak signal, and a CPU that calculates a distance or a relative speed to a target object based on the corrected frequency (f.sub.n+.delta.). In an FFT calculation section, the frequency (f.sub.t) of the true peak signal is calculated based on the characteristic of a window function, and if the frequency (f.sub.t) thus calculated is determined as an incorrect estimation, the frequency of the true peak signal is further corrected.