1. A marker processing method comprising: (a) binarizing a shot image; (b) labeling one or more constituents of the image detected based on the image binarized in step (a); (c) obtaining a region centroid of each of the constituents corresponding to the respective labels processed in step (b); (d) obtaining a degree of overlap of the region centroids of the constituents corresponding respectively to the labels, obtained in step (c); and (e) detecting a marker based on the degree of overlap of the region centroids obtained in step (d).