1. An autonomous vehicle comprising: a scanning point acquisition unit scanning a predetermined space at a constant angle or a constant interval with using an electromagnetic wave or an acoustic wave, receiving reflected waves from objects existed in the horizontal plane, and acquiring coordinates of a plurality of scanning points from which the electromagnetic wave or the acoustic wave is reflected; an element vector forming unit forming an element vector with respect to two scanning points selected among the plurality of scanning points so that one scanning point acquired earlier in time series by the scanning point acquisition unit is used as a start point of the element vector and another scanning point acquired later is used as an end point of the element vector; an element vector selecting unit selecting a plurality of element vectors which are continued in time series of order of formation by the element vector forming unit, length of each element vector being equal to or shorter than a first predetermined length, a deflection angle of an element vector with respect to another continuing element vector being equal to or smaller than a first predetermined angle, and an integrated value of the deflection angles being equal to or smaller than a second predetermined angle; a scanning segment vector forming unit forming one scanning segment vector by composing the selected continuing element vectors; and an obstacle recognizing unit comparing a segment defined by a start point and an end point of the scanning segment vector with a second predetermined length, and recognizing that a planar obstacle exists along the scanning segment vector when the segment is equal to or longer than the second predetermined length.