An object detection post-processing device of a display device, includes: an input to receive position information of an object that is detected from input image data for the display device in a current frame; a position information storage device to accumulatively store the position information of a plurality of previous frames; an accumulated position calculator to generate accumulated position information according to the position information of the current frame and the position information of the plurality of previous frames; and a position information determiner to determine final position information according to the accumulated position information, and to output the final position information.