The present invention provides an apparatus and method for correcting an inspection reference pattern image in order to properly inspect a pattern image of a specimen. The pattern image correcting apparatus is characterized by including: a first pattern synthesizing unit for synthesizing an assist pattern image and a pattern image to be inspected, thereby generating a pattern image to be inspected with an assist pattern; an assist pattern shift processor; a second pattern synthesizing unit for synthesizing the shifted assist pattern image and the inspection reference pattern image, thereby generating an inspection reference pattern image with an assist pattern; a model generating unit for generating a position shift model by using the pattern image to be inspected with the assist pattern and the inspection reference pattern image with the assist pattern; and a correction pattern image computing unit for correcting the inspection reference pattern image.