1. A vehicle surroundings monitoring apparatus including: a radar for scanningly irradiating electromagnetic waves over a predetermined angular range around a subject vehicle on which said apparatus is mounted, detecting the electromagnetic waves reflected from objects lying around said subject vehicle, and outputting a plurality of directions of scanning irradiation and detected distances from said subject vehicle to said objects in the respective directions of scanning irradiation; and a recognition unit for outputting, based on the detection results of said radar, a relative position and a relative speed, or a rate of change of the relative position, of each of said objects lying around said subject vehicle with respect to said subject vehicle; said recognition unit comprising: a detection points data storage section for storing therein whether or not detection points data in the form of a data pair comprising a direction of scanning irradiation and a detected distance in that direction output by said radar exists in each of M×N small regions into which X, Y coordinates with an X axis being set in a widthwise direction of said subject vehicle and a Y axis being set in a running direction of said subject vehicle are divided, in a two-dimensional array including a plurality of elements corresponding to the small regions, respectively; and an object detection section for performing arithmetic operations of multiplication and summation of the respective elements of said two-dimensional array representative of the presence or absence of the detection points data stored in said detection points data storage section while sequentially scanning a mask of a two-dimensional array comprising J×K (J<N, K<M) elements, and determining, based on the results of the arithmetic operations, attributes such as positions, sizes, etc., of said objects lying around said subject vehicle.