PURPOSE: To obtain a car speed corresponding to a throttle operating quantity regardless of a road surface condition by converting an accelerator operating quantity by a certain functional relation, to make it a car speed commanding value, and feedback controlling a car speed in accordance with a deviation.

CONSTITUTION: When a car is traveling, a car speed commanding signal corresponding to the operating quantity of an accelerating means 51, is generated from a function generating means 53 in accordance with the output of an operating quantity detecting means 52, which outputs a signal corresponding to the operating quantity of the accelerating means 51, and is inputted together with an actual car speed signal from a car speed detecting means 54, into a controlling means 55. Here, a deviation between both inputted signals is detected, and a controlling signal corresponding to the deviation is outputted to the throttle driving means 56, to control a throttling means 57, as appropriate, and restrict the car speed to a predetermined value. In this case, a variable function generating means, in which a function characteistic can be varied in accordance with the operation of a data inputting means including a push button switch, is also available instead of the function generating means 53.