To accurately estimate the shape of the eyeball tissue by receiving an eyeball image of a user, detecting boundary position information of the eyeball tissue in the eyeball image, performing a prescribed weighted calculation in relation to the boundary position information, and estimating the shape of the eyeball tissue using the weighted boundary position information.

An image of the eyeball 1 lighted by an infrared emission diode 2 is picked up by an image-formation optical system 3 and an area sensor 4 so as to output an analog image signal row 6. Secondly, in a microcomputer 5, the analog signal row is A/D converted, the converted results 7 are stored in a RAM, and the digital image data row is provided. The signal is processed in relation to the image data row in the RAM, a pair of reflecting images of the cornea and a plurality of the pupil edges are detected, and their coordinates are stored. Thirdly, the pupil circle is estimated by the least square operation weighted according to changes in the signals (luminance) of the pupil edge part based on a plurality of coordinates of the pupil edges, and the eyeball rotation angle is calculated based on its central coordinate and the coordinates of the cornea reflecting images.