1. An image processing apparatus for detecting noise in a digital image of an eye, comprising: a calculation part calculating the average brightness value of each of multiple pixels in said digital image overlapping with a curve having a shape substantially conforming to the rim of the eyelid of said eye at each position of said curve while moving said curve from near the center of the pupil of said eye to said eyelid on said digital image; and an identifying part identifying the position of noise contained in an image of said iris in said digital image based on the degree of change in said average brightness value at said position.