A plurality of workpieces include a plurality of first workpieces of a first workpiece group to be loaded onto a first loaded member according to a first loading sequence and a plurality of second workpieces of a second workpiece group to be loaded onto a second loaded member according to a second loading sequence. On a conveying device, workpieces are arranged at ransom with respect to respective arrangement sequences of the first workpiece group and the second workpiece group and the classifications of the first workpiece group and the second workpiece group. On a conveying device, workpieces of the first workpiece group are sequentially arranged based on the first loading sequence and workpieces of the second workpiece group are sequentially arranged based on the second loading sequence. At the same time, the workpieces of the first workpiece group and the second workpiece group are arranged together.