PURPOSE: To execute follow-up traveling well-adapted to the environment, and to prevent hunting, etc., even under such an undesirable environment as a preceding car is dirty and deterioration of the performance of a radar equipment is invited, in the vehicle traveling controller which follows the preceding car.

CONSTITUTION: Detecting signals from a radar equipment 10 and a car speed sensor 12 are supplied to an ECU (electronic controller unit) 14, and by controlling a throttle actuator 16 or a brake actuator 18 so as to hold a safe inter-car distance, this controller travels by following a preceding car. Even at the time of fine weather, when snow is melting, a body of a vehicle becomes dirty, therefore, the detecting performance of the radar equipment 10 is deteriorated, but the ECU 14 evaluates a degree of dirt of the preceding car from an inter-car distance and reflection intensity detected by the radar equipment 10, and calculates a ratio of the dirty preceding car for the total number of detected preceding cars. The ECU 14 sets lowly the acceleration gain of follow-up traveling in accordance with the ratio, and transfers to gradual follow-up traveling.