An evaluation method of wrinkle shapes on fabrics using simple morphological operations is proposed. It calculates the size density function of the object indicating the region surrounded by a folded fabric in the experimental condition of the standard wrinkle/crease angle test. The characteristics of the size density function and the parameters of the linear and cubic function fitted to the size density function indicate the fabric shape characteristics, which correspond to visual edge sharpness and roundedness of pleat lines, as well as their mechanical properties.