1. A driving assisting apparatus comprising: a detection means for detecting an obstruction near a vehicle by radiating a wave to the surroundings and receiving the wave reflected by the obstruction; and an assisting means for assisting driving of the vehicle when the detection means detects an obstruction, wherein the detection means has: a plurality of distance measurement means each provided at predetermined intervals on the vehicle in a vertical direction and each used for measuring a distance to an obstruction based on time taken by the wave to propagate to the obstruction, hitting the obstruction and to propagate back; a height computation means for computing a height of an obstruction from a surface of a road by using the distance measured by each of the distance measurement means as a parameter representing a distance to the obstruction in accordance with calculation conditions set in advance based on installation positions of the distance measurement means on the vehicle; and an inhibition means for comparing the computed obstruction height from the surface of a road with a threshold height representing an upper limit of heights of bodies each not becoming as an obstacle to a travel motion of the vehicle to determine whether the computed obstruction height is smaller or greater than the threshold height and inhibiting an operation of the assisting means for a computed obstruction height found smaller than the threshold height.