1. A driving assisting system for an own vehicle, comprising: a detector configured to detect at least one of an operation status of the own vehicle and a running environment around the own vehicle; a risk potential calculating device configured to calculate risk potential associated with the own vehicle based on a detection result of the detector; a driver's intention detecting device configured to estimate a driver's intention; an acceleration necessity judging device configured to judge necessity for acceleration; and a data processor configured to determine a reaction force to be transmitted to a driver from an accelerator pedal based on the calculated risk potential, the estimated driver's intention and the necessity for acceleration, in response to the estimated driver's intention being a predetermined type of intention.