In this bottle can manufacturing method, when a portion located at the skirt portion 7 is being molded, the portion extending in an opposite direction in which the male threaded portion 6 extends from a lower end 6a of the male threaded portion 6 over a range of at least approximately 180° along a circumferential direction of the skirt portion 7, the inner surfaces of molding pre-form portions of the first circumferential wall portion and the convexly curved surface portion from among the molding pre-form portions of the skirt portion 7 are pressed outward in the radial direction of the bottle can body.