A method for manufacturing a seat cushion material, the seat cushion material including a front layer part and a back layer part having a back side surface, the method including: preparing for molding the seat cushion by attaching the back layer part to an upper die having an upper cavity surface; molding the seat cushion material by adding foamed resin raw material forming on a lower cavity surface of a lower die and then by closing the upper die to which the back layer part is attached, the lower cavity surface being provided with a plurality of protrusions which is configured to be brought into contact with a seating surface side of the back layer part and press the back layer part against the upper cavity surface when the upper die to which the back layer part is attached is closed; and demolding the molded seat cushion material.