To facilitate the separation of a cup single unit one by one from a stacked body of a large number of the cups by forming a downward tapered-in peripheral surface by partially drawing inward the smaller diameter periphery of the cup side plate which is tapered out upward, and at the same time, bonding a round tray shape bottom paper to the internal surface of the downward tapered-in peripheral surface by the erected peripheral surface of the bottom paper, and thus, preventing a large number of sticking-out protrusions from coming into contact with the internal surface of the cup which is stacked on the outside, even when there are the large number of sticking-out protrusions due to an unevenness of a vertical crimping superposition, caused by the draw-erecting of the bottom paper erected peripheral surface on the external surface of the downward tapered-in peripheral surface of the side plate in the bottom paper peripheral edge.

A blank 1 for which a mechanical woodpulp paper is formed into an approx. arc-form rectangular shape, is rounded in the length direction, and the end sections 1a are bonded to each other with a bonding section 2. Thus, a hollow truncated conical-shaped cup side plate 3 is formed. Then, when this paper cup wherein a bottom paper is bonded to the smaller diameter end section of the cup side plate 3 is manufactured, a tapered-in peripheral surface 4 is formed by partially drawing the smaller diameter peripheral 3a of the cup side plate 3. At the same time, a round tray-shape bottom paper 5 is bonded to the inner peripheral surface of the end section of the peripheral surface 4, by the erected peripheral surface 6 of the bottom paper 5.