The present invention relates to a molding die for molding a hollow molding article, including: a pin plate having an inflow port for molding material, a tubular bushing forming a molding path continued from the inflow port, an outlet of the die positioned in the extending direction of the molding path, a conical pin provided perpendicularly to the pin plate and disposed inside the molding path, a gap, that is continuous in the longitudinal direction, being provided between an inner wall surface of the molding path and an outer surface of the conical pin, an adjusting device for adjusting a width of a standard annular gap when a gap formed between a specified position in the longitudinal direction of the molding path and the outer surface of the conical pin opposing to the position.