In an object detection apparatus, a range image generator, based on distance information indicative of distances from a given measurement point to objects in real space, generates a range image indicative of a distribution of distance information of objects located around the measurement point. A subgroup generator horizontally divides the range image into a number of column regions of prescribed width, and for each column region, generates one or more subgroups that extend continuously in a vertical direction of the range image and fall within a given range of distance information. A continuity determiner determines, for each of the subgroups, whether or not there is distance continuity between the subgroup and its horizontally adjacent subgroup in the range image. A merger merges together horizontally continuous-in-distance subgroups. An object detector detects an object in each of regions of the range image corresponding to the respective merged groups.