Abstract: A graphic display device displays a three-dimensional polyhedral object on a two-dimensional screen in accordance with hidden surface processing. The device includes a plurality of pixel processors corresponding to each of the pixels on one scan line on the screen. The hidden surface processing device includes an error register which stores data relating to errors of a plane segment on one scan line nearest to pixels at its boundaries and error information indicating whether an error is due to a left boundary or a right boundary, and an error data bus which reads the storage contents of the error register together with luminance data. The hidden surface processing device obtains luminance data relating to a plane to be displayed at high speed. The luminance data and the boundary error data are used for anti-aliasing processing. An anti-aliasing method executes corrections for boundaries of the pixels using two successive pixels on one scan line.