1. An object detecting apparatus for a vehicle, the object detecting apparatus comprising: transmitting/receiving means for transmitting an electromagnetic wave in a driving direction of the vehicle at predetermined intervals and for receiving a reflected wave from an object, the transmitting/receiving means installed in the vehicle; object candidate position detecting means for detecting a position of an object candidate based on a result of the transmission and reception performed by the transmitting/receiving means; unifying means for unifying a plurality of object candidates into a single group in a case where the plurality of object candidates are detected within a predetermined unified range; group representative point calculating means for calculating a representative point of the group unified by the unifying means; tracking means for judging whether there is continuity between a group made in a previous detection cycle and a group made in a current detection cycle based on the group representative point calculation; object information outputting means for outputting a representative point of a group after a split, based on an output from the group representative point calculating means and an output from the tracking means; unified information storage means for storing the object candidates forming each group; and running lane estimating means for estimating a running lane in which the vehicle runs, wherein in a case where a change in relative positions of the plurality of object candidates of the single group splits the single group into a plurality of split groups whose representative points are present in different lanes, the tracking means judges whether any of the object candidates forming the group before the split continuously remains to be detected in a running lane including the representative point of the group before the split based on an output from the unified information storage means and an output from the running lane estimating means, and in a case where any of the object candidates forming the single group before the split is determined as continuously remaining to be detected in the running lane, the tracking means determines there is continuity between the group after the split including the thus-determined object candidate and the group before the split.