To make many stacked cups easily slidable and a single cup easily separable one by one from a stacked body of many cups.

A substantially arc-shaped and short strip-like blank 1 for a side cylinder is rounded in its lengthwise direction, and ends 1a of the rounded blank are bonded to each other at a bonding part 2 to form a hollow and truncated cone-shaped cup side cylinder 3. In forming a cup in which a bottom paper 4 is bonded to the small-diameter peripheral surface 3a of the cup side cylinder 3, many flaps 5 are formed on an outer periphery of a substantially circular bottom paper blank, and a substantially circular notch 6 is respectively formed in each valley among the respective flaps 5. Each flap 5 is upwardly folded from a substantially central portion of each notch 6 to form a flap rising piece 5b, thereby forming the substantially round pan-like bottom paper 4 in which a notch peripheral part 5c of each rising piece 5b is rounded in the peripheral direction of the side cylinder along a folded arc-like edge side 6a of each notch 6. By bonding the small-diameter peripheral surface 3a of the cup side cylinder to the flap rising pieces 5b of the bottom paper, the peripherally rounded state of the small-diameter peripheral surface 3a is smoothly maintained.