The method comprises the steps of: preparing a first suction-holding section and a second suction-holding section； positioning the first suction-holding section and the second suction-holding section in such a manner that respective surfaces of the first suction-holding section and the second suction-holding section are aligned side-by-side while facing the same side； suction-holding a forward surface of a main body of an developed module by the first suction-holding section, and suction-holding a rearward surface of the main body of the developed module by the second suction-holding section； closing the first suction-holding section and the second suction-holding section to fold the main body in half； and releasably joining superimposed portions of the developed module half-folded by the half-folding step.
