1. An object detection apparatus which is mounted in a vehicle and detects an object in a surrounding area of the vehicle, the apparatus comprising: a radar device which detects an object in the surrounding area of the vehicle as a dot; a processing part which calculates, from a result of the detection as the dot by the radar device with respect to a target which is the object detected by the radar device, information indicating a relative position of the target relative to the vehicle, or information indicating the relative position of the target relative to the vehicle and at least one of a relative distance and a relative speed of the target relative to the vehicle, as target information; a traveling direction prediction part which predicts a traveling direction of the vehicle, and predicts a traveling direction of the target based on the target information calculated by the processing part; a determination part which determines, from the target information calculated by the processing part and the traveling direction of the target predicted by the traveling direction prediction part, whether a condition (i) that the relative position of the target indicated by the target information is within a set area which is set to a side strip at a lateral side of the vehicle and a condition (ii) that the traveling direction of the target predicted by the traveling direction prediction part is not a direction toward where the vehicle is heading are satisfied for each target, and which determines that the target is a movable body which does not collide with the vehicle when the conditions are satisfied; and a collision determination part which determines whether the target, that has been determined by the determination part as not being the movable body which does not collide with the vehicle, is likely to collide with the vehicle, wherein the determination part accumulates, each time the determination part has determined that the conditions are satisfied for the target, the number of times when the determination part has determined that the conditions are satisfied for the target and determines, when the accumulated number has reached a predetermined number, that the target is the movable body which does not collide with the vehicle, the travelling direction prediction part predicts the traveling direction of the target only when a predetermined number of chronological pieces of target information of the target are stored in a target information memory, and the processing part, the travelling direction prediction part, the determination part, and the collision determination part are executed by a computer.