1. A similar shape retrieval apparatus, comprising: a shape model inputting unit; a query shape inputting unit for providing a query shape model; a shape model meshing unit for meshing a shape model to obtain a shape mesh model including a plurality of mesh elements on a surface of the shape model; a partial characteristic shape mesh model extracting unit for calculating an inner product of normal vectors of adjacent mesh elements in said shape mesh model, setting a line between the adjacent mesh elements as a boundary line of different surface groups of mesh elements respectively including the adjacent mesh elements when the calculated inner product of normal vectors of the adjacent mesh elements is a threshold value or less, and extracting a partial characteristic shape separately for the different surface groups; a partial characteristic amount calculating unit for calculating a characteristic amount of the partial characteristic shape mesh model using a barycenter distance between mesh elements and normal vectors of said mesh elements in said partial characteristic shape mesh model; a searching unit for searching for a part of said shape model similar to said query shape model based on the characteristic amount of the partial characteristic shape mesh model; and a display part for displaying any one of the query shape model and the searched part of the shape model which is determined to be similar by said searching unit.