A vehicular radar apparatus comprising a radar beam transmission device and a reception device, and a processing unit for detecting the position of a target object from transmission signals and reception signals. The processing unit has a preceding vehicle judgment circuit for judging if a vehicle travelling in front of a subject vehicle in the same direction is the same vehicle as previously detected or not, and a signal strength comparing device for comparing the signal strength of a current reception signal reflected from the preceding vehicle, with a signal strength of a reception signal reflected from the preceding vehicle a predetermined comparison reference time prior, to thereby calculate a change amount in signal strength. When the change amount calculated by the signal strength comparing device drops beyond a previously set threshold value and it is judged by the preceding vehicle judgment device that the preceding vehicle is the same vehicle, it is judged that the detection sensitivity of the radar apparatus has dropped.