1. A pattern-defect analysis equipment, comprising: a surface-observation-image acquisition unit for acquiring a surface observation image of a partial region on surface of a substrate on which patterns of a plurality of layers are formed; and a data processing unit for storing design data about configurations of said patterns formed in each layer of said substrate, and judging criticality of a pattern defect included in said surface observation image of said partial region of said substrate acquired by said surface-observation-image acquisition unit; wherein said data processing unit acquires, via said surface-observation-image acquisition unit, a surface observation image of said partial region in a layer that includes said pattern defect, said partial region including said pattern defect, compares said acquired surface observation image with a predetermined reference image, and thereby extracts an image of said pattern-defect portion as a defect image from said surface observation image, said predetermined reference image including no pattern defect, performs an alignment between a self-layer design pattern image and said surface observation image by performing an image matching between said self-layer design pattern image and said surface observation image, said self-layer design pattern image being generated from said design data, said design data belonging to a layer which is identical to said layer that includes said pattern defect with respect to said partial region corresponding to said surface observation image, generates a first synthesized image based on result of said alignment, said first synthesized image being generated by synthesizing said defect image with an another-layer design pattern image, said another-layer design pattern image being generated from said design data, said design data belonging to a layer which is different from said layer that includes said pattern defect with respect to said partial region corresponding to said surface observation image, determines data based on said first synthesized image, said data indicating a first relative position relationship between said pattern defect and a pattern, said pattern belonging to said layer which is different from said layer that includes said pattern defect, and judges said criticality based on said determined data indicating said first relative position relationship, said pattern defect exerting said criticality on said pattern, said pattern belonging to said layer which is different from said layer that includes said pattern defect.