1. A method for directional counting of moving objects at a prescribed monitoring target location, comprising the steps of: (a) taking sequential images of the prescribed monitoring target location; (b) setting a counting line in an image field of the sequential images, and acquiring a dynamic image formed by time changing pixel values of a series of pixels forming the counting line from each sequential image; (c) obtaining a background image by successively updating the pixel values of the series of pixels forming the counting line in states in which a moving object is not passing over the counting line; (d) applying a subtraction processing on the dynamic image and the background image, and then applying a binarization processing to extract a moving object region; (e) forming a moving object image by sequentially labeling moving object region in time order; (f) counting a number of moving objects passing through the prescribed monitoring target location according to the moving object image; and (g) setting upper and lower direction judgement regions above and below the counting line in the image field of the sequential images, and judging a passing direction of each moving object by judging one of the upper and lower direction judgement regions in which the moving object is present at a time of a formation start/end time of the moving object image.