In a vehicular velocity controlling system and method, a vehicular velocity control is performed in such a manner that an inter-vehicle distance of a host vehicle to a preceding vehicle is substantially made equal to a target inter-vehicle distance during a presence of the preceding vehicle and in such a manner that the vehicular velocity is substantially made equal to a set vehicular velocity during an absence of the preceding vehicle, a frictional coefficient of a road surface on which the host vehicle is running or about to run is detected, an upper limit value for the vehicular velocity control is set in accordance with the detected road surface frictional coefficient, below the upper limit value of which the vehicular velocity control is enabled to be performed in such a manner that as the road surface frictional coefficient becomes lower, the upper limit value becomes lower.