A radar apparatus is mountable on a vehicle, transmits a radar signal, and includes a radio receiver that receives reflected wave signals being the radar signal reflected by multiple objects present in the viewing angle of the radar apparatus via a receiving antenna mountable on a side of the vehicle, a signal processing unit that determines the azimuths of the objects, the Doppler speeds between the radar apparatus and the objects, and the intensities of the reflected wave signals by using the reflected wave signals, and a radar state estimation unit that estimates the speed and traveling direction of the radar using the azimuths of the objects, the Doppler speeds, and the intensities.