A foam forming die, comprising a filter port, a hollow part, and an exhaust flow passage, wherein two rotating bodies having an outer peripheral section formed generally in complete round shape are disposed at the end of the flow passage and the end part of the flow passage is narrowed by the rotating bodies to form a molten resin discharge part, and the rotating bodies are rotated in a molten metal discharge direction to control the flow of molten resin, whereby, since a shear heating can be reduced while maintaining a pressure inside the die at a high pressure, the temperature of the molten resin can be adjusted easily and the flow of the molten resin can be uniformized and, accordingly, since a large amount of foam agent with low solubility can also be used, the various types of hard-to-foam resin materials can be foamed easily.