This paper proposes a method for generating smocking patterns of twist folds for clothing design. Smocking is a handcraft technique of sewing and making pleats over cloths, and has been used to produce decorations over the surface of cloths. However, it is not easy to generate the pattern for the desired shape on the surface of flexible cloths. For the type of smocking which corresponds to twist fold in Origami, we propose to sew down the intersection of folded pieces of cloth so that the formed shape can be kept on the cloths, and propose a method for generating smocking patterns of twist folds. The proposed method is based on the geometric transformation of polygons in crease patterns, and its geometric characteristics are clarified. The proposed method is implemented using GeoGebra, and it is validated in terms of a newly designed smocked clothing based on the generated patterns.