In automatic vehicular velocity controlling apparatus and method for automotive vehicle, a target vehicular velocity to maintain a predetermined inter-vehicle distance between a preceding vehicle which is running ahead of the vehicle is set as a first set vehicular velocity and a vehicular velocity of the vehicle (host vehicle) is controlled to give one of the first set vehicular velocity and a second set vehicular velocity by a manual setting through a set switch and an accelerate switch or coast switch if the preceding vehicle is present and is controlled to maintain the vehicular velocity at the second set vehicular velocity if no preceding vehicle is present. Then, when the set vehicular velocity is modified through the above-described accelerate switch or coast switch, a vehicular velocity variation rate is determined in accordance with a deviation between the actual vehicular velocity and a newly set vehicular velocity after the modification of the vehicular occupant's vehicular velocity.