1. An image processing method for searching a region that matches a model registered in advance from an input image, the image processing method comprising: a step of registering an edge code histogram generated from a plurality of edge codes contained in a model image; a step of setting a first region of interest with respect to the input image; a step of generating an edge code histogram for the first region of interest; a step of sequentially changing a relative positional relationship between the edge code histogram of the model and the edge code histogram for the first region of interest and sequentially calculating a degree of coincidence between the edge code histograms at each relative position; a step of evaluating a possibility that the region that matches the model is contained in the set first region of interest from the sequentially calculated degree of coincidence between the edge code histograms; and a first specifying step of sequentially changing the center position of the first region of interest with respect to the input image and repeating the generating step, the calculating step, and the evaluating step for each first region of interest to specify a candidate point having a possibility of matching the model in the input image.