PURPOSE:To provide the preceding vehicle approaching warning device capable of alarming the stopped preceding vehicle at a proper timing. CONSTITUTION:A radar device 21 detects the distance between two cars, an information processing circuit 25 calculates the relative speed between the self vehicle and the preceding vehicle as the differential value of the distance between two cars. The warning distance is calculated according to the relative speed and a car speed signal from a car speed sensor 23. When the distance between two cars becomes shorter than the warning distance, a warning generating device 27 gives a warning. The information processing circuit 25 calculates the relative speed based on the plural detection values of the distance between two cars. When the frequency of detections is less than the prescribed one, the same value as the self car speed is defined as the relative speed. In short, the preceding vehicle is considered as being stopped. Accordingly, the discrimination is performed by using the longer warning distance for the stopped vehicle and even when the preceding vehicle is stopped, the proper alarm can be given at early timing.
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