1. A blur direction judgment method comprising the steps of: obtaining one or more weighting parameters for one or more statistical characteristic quantities representing a direction of blur in a predetermined structure in an input image by fitting a model representing the structure to the structure in the input image, the model having been obtained by carrying out predetermined statistical processing on a plurality of images representing the predetermined structure in different conditions of blur, and the model representing the structure by one or more statistical characteristic quantities including the statistical characteristic quantity or quantities representing the direction of blur and by one or more weighting parameters for weighting the statistical characteristic quantity or quantities according to an individual characteristic of the structure; and judging the direction of blur represented in the input image according to a value or values of the weighting parameter or parameters having been obtained.