PURPOSE: To provide a precaution radar for vehicle in which the tracking is conducted by detecting the rough distance to an obstacle and a transition of tracking is made quickly to a new obstacle is the new obstacle is detected at a distance closer than the old obstacle by searching.
CONSTITUTION: A transmission antenna 13 transmits a signal forward. A searching channel 3 searches the receiving signal from a receiver 22 for the reflection wave from an obstacle under control of a control operating unit 51. Rough distance between a vehicle and obstacle is also obtained based on the time lag of reflection signal behind the transmission signal by searching within a predetermined range. When the rough distance is obtained, the control operating unit 51 controls the searching channel 3 to repeat searching while setting a searching range within the rough distance when viewed from the vehicle. At the same time, a tracking channel 4 tracks the reflection signal from the obstacle based on the rough distance thus obtained and detects the precise distance between the vehicle and the obstacle.