An aligning prism amount determination device to determine an aligning prism amount for correcting fixation disparity of a spectacle wearer, having the fixation disparity, includes a determiner (11) to determine an aligning prism amount to be uniformly included in the spectacle lens for correcting the fixation disparity, based on a first aligning prism amount obtained by measuring an aligning prism amount of the spectacle wearer at an eye examination distance corresponding to a first distance, a second aligning prism amount obtained by measurement at an eye examination distance corresponding to a second distance shorter than the first distance, and information used for allocation of the first aligning prism amount and the second aligning prism amount, within a prism prescription range between the first aligning prism amount and the second aligning prism amount.
