1. A pattern shape evaluation method comprising: acquiring an image of an evaluation target pattern including a plurality of element patterns; detecting edge of the evaluation target pattern from the image; classifying the detected edge of the evaluation target pattern into a plurality of evaluation target pattern edge groups; acquiring edge of a reference pattern serving as an evaluation standard for the element patterns; classifying the edge of the reference pattern into a plurality of reference pattern edge groups; selecting a reference pattern edge group to be aligned with the edge of the evaluation target pattern from the classified reference pattern edge groups; aligning the edge of the selected reference pattern edge group with the edge of the evaluation target pattern; and evaluating the shape of the evaluation target pattern by use of the result of the alignment.