PURPOSE: To prevent rapid acceleration/deceleration by calculating acceleration from output information of a car speed sensor, and outputting control information with the acceleration in a preset range, in the case of outputting the control information of adjusting a car speed so as to obtain an intervehicle distance in the prescribed value or more.

CONSTITUTION: In a program control circuit 3, when autocruise control is set, a vehicle is made to run at a fixed speed. A detection value from an intervehicle distance sensor 1 is input, to confirm whether the detection value exceeds a lower limit value or not. In the case that the detection value is the lower limit value or less, by excessively approaching a leading vehicle, an alarm is generated to execute automatic decelerating control, so as to return to a process of fetching an intervehicle distance. On the other hand, when the detection value exceeds the lower limit value, the alarm is released, and a detection value from a car speed sensor 2 is input, to calculate acceleration for the detection value. As a result, when the calculated acceleration is a lower limit value or less, a control valve 4 is controlled to increase an injection amount of fuel supplied to an internal combustion engine.