1. An image processing apparatus that specifies a position of a predetermined characteristic portion of a target face image, the image processing apparatus comprising: an initial disposition unit that determines an initial disposition of a characteristic point of the target face image based on a disposition of the characteristic point of a reference face image that is set based on a statistical analysis on a plurality of sample face images of which dispositions of the characteristic points representing the positions of the characteristic portions are known; an image transforming unit that performs a first transformation for at least one of the reference face image and the target face image, so that disposition patterns of the characteristic points of the reference face image and the target face image are identical to each other; a normalization unit that performs a first normalization process, in which predetermined first index values that represent distributions of pixel values of the reference face image and the target face image approach each other, for at least one of the reference face image and the target face image after the first transformation; a determination unit that compares the reference face image with the target face image after the first normalization process and determines whether to update the disposition of the characteristic point of the target face image based on a result of the comparison; and an update unit that updates the disposition of the characteristic point of the target face image based on the result of the comparison between the reference face image and the target face image in a case where the update is determined to be performed.