1. A stereoscopic image processing apparatus for calculating a parallax between a pair of stereographic images, comprising: correlation evaluating means for evaluating a correlation of brightness between a first pixel block provided in one of said pair of stereographic images and a second pixel block provided in the other of said pair of stereographic images; and region size changing means for changing a size of said first and second pixel blocks for said correlation evaluating means, wherein a size of said first and second pixel blocks is changed in accordance with an area where said first pixel block is located in the respective pair of images.