1. An image processing method for detecting the positions of a plurality of landmarks that indicate the shape of a predetermined subject by their positions and/or their positional relationships, from within the predetermined subject included in an image, comprising the steps of: setting the positions of a plurality of landmarks that indicate the average shape of the predetermined subject as preliminary positions of the landmarks included in the predetermined subject included in the image; calculating characteristic amounts, which are defined for a landmark corresponding to a preliminary position, of each pixel within a range of pixels that includes the preliminary position to discriminate the landmark; judging whether pixels that represent the landmark are included in the range, by discriminating whether each of the pixels within the range represents the landmark; moving the preliminary position to approach the position of the pixel which has been discriminated to represent the landmark, in the case that the judgment is affirmative; repeating the preceding three steps for all of the preliminary positions; and determining the positions of the preliminary positions after they have been moved to be the positions of the landmarks that correspond to each of the preliminary positions; the discrimination regarding whether the pixels represent the landmarks being performed, based on learning characteristic amounts of positions, which are known to represent the landmarks, and characteristic amounts of positions, which are known to not represent the landmarks, of a plurality of sample images by a machine learning technique.