1. An image processing apparatus comprising: an image pickup unit; and a processing device including: an image processing accuracy estimation unit which estimates an image processing accuracy by calculating a size of an object by which the accuracy of measurement of the distance of the detection object photographed by said image pickup unit becomes a permissible value or less; an image post-processing area determination unit which determines, in accordance with the image processing accuracy estimated by said image processing accuracy estimation unit, a partial area inside a detection area of the detection object as an image post-processing area in which an image post-processing is carried out and lattices the determined image post-processing area to cells; an image processing unit which processes the image photographed by said image pickup unit to detect a recognition object; and an image post-processing unit which determines the presence/absence of the detection object by calculating, in respect of the individual cells inside the latticed area determined by said image post-processing area determination unit, the probability as to whether the recognition object detected by said image processing unit is present in each of the individual cells and the probability as to a direction in which said recognition object moves in each of the individual cells.