A pedestrian determining system mounted on a vehicle determines a collision object for protecting a pedestrian. An impedance sensor is included for detecting an alternating-current impedance or an electricity quantity being a function value of the alternating-current impedance to thereby output the detected one as an impedance signal, wherein the alternating-current impedance is varied by approaching of the collision object. A collision load sensor is included for detecting a collision load when the collision object collides with the vehicle to output the detected collision load as a collision load signal. Whether the collision object is a pedestrian or not is determined based on a value of a given function including as input variables the impedance signal outputted from the impedance sensor and the collision load signal outputted from the collision load sensor.