1. An image processing apparatus that corrects an image of an eye defined by a plurality of lines belonging to a first line group and a second line group located adjacent to each other, the image being picked up through an interlaced scheme and the image processing apparatus comprising: a calculating unit which moves the second line group relative to the first line group predetermined amount by predetermined amount, and which calculates, for each pixel belonging to the first line group among pixels configuring an image of a pupil of the eye, a difference in brightness between a pixel belonging to the first line group among pixels configuring the image of the pupil of the eye and a pixel belonging to the second line group and adjacent to the pixel belonging to the first line group; an integrating unit that integrates brightness differences calculated pixel by pixel; and a correcting unit that corrects misalignment between the first line group and the second line group based on a relative displacement of the second line group to the first line group when an absolute value of an integrated value obtained by the integrating unit becomes minimum.