1. A pattern correction apparatus for performing proximity effect correction with regard to a design pattern, said apparatus comprising: an information inputting section; a correction calculation section; and an information outputting section, wherein, said correction calculation section: performs optical proximity effect correction by calculating a two-dimensional model-based optical proximity effect correction for each of a plurality of sampling points set on at least one pattern edge which forms the design pattern; performs process proximity effect correction calculation by weighting with a two-dimensional distribution of the pattern edge around each said sampling point; said weighting being performed such that a high weight is applied to a region in which reaction products which can have an influence on the sampling point but a low weight is applied to any other region, and uses, in a function to be used for the correction calculation by the two-dimensional model-based optical proximity effect correction, a peripheral pattern area density value as an argument and integrates an integration kernel produced arbitrarily and a peripheral pattern distribution to calculate the peripheral pattern area density value, and then reflects an influence of the weighting on a result of the calculation.