1. An object detection apparatus comprising: a camera which acquires a plurality of frames in a time-series manner; a first detector configured to detect a predetermined object in each of the frames; a determination unit configured to store detection results corresponding to the frames, to compare a first detection result corresponding to a first frame of the frames with a second detection result corresponding to a second frame of the frames acquired after the first frame, and to determine whether a false negative of the predetermined object exists in the second frame; and a second detector configured to detect the predetermined object in the second frame when it is determined that the false negative of the predetermined object exists, the second detector differing in performance from the first detector.