pleat pieces 22 and the corresponding right side edge portion b of the inner pleat pieces 23 are sewed together along their contours and each left side edge portion a of the outer pleat pieces 22 and the corresponding left side edge portion a of the inner pleat pieces 23 are sewed together along their contours as shown in fig3 and 4 thus the fabric pieces 21 are tidily joined together along the contours of the opposite side edge portions the side edge portions a b a and b of the fabric pieces 22 and 23 may be stitched together in any ways as long as they will not frayed and the stitch type is appropriately selected from running stitch reverse stitch overcast stitch blind stitch and other stitches a core such as wire may be inserted along the contours in order to prevent the pleat from losing its curved contour the fabric pieces 21 may be joined together by crimping using an adhesive instead by sewing next the joined outer pleat pieces 22 and inner pleat pieces 23 are folded along the contours of the sewed side edge portions a b a and b here the joined fabric is folded to alternate between mountain folds and valley folds thus the outer pleat pieces 22 are arranged on the outer side and the inner pleat pieces 23 are arranged on the inner side as shown in fig1 thereby forming the curved pleat 2 in the embodiment the folded fabric is pressed to put folds.