The purpose of the present invention is to provide a method to efficiently make flaskless upper and lower molds, to efficiently spray a release agent in a closed space, and to promptly place a core. The invention is a method for making flaskless upper and lower molds that are stacked, comprises the steps of holding a match-plate between one pair of cope and drag flasks that are horizontally positioned, each of them having an sand-filling port for supplying molding sand at its side wall, defining upper and lower molding spaces by inserting upper and lower squeeze-plates to the respective openings of the pair of cope and drag flasks which openings are opposed to the match-plate, putting the pair of cope and drag flasks and the match-plate in a vertical position, and causing the sand-filling port to be placed in upper position, spraying a release agent to the two molding spaces in upper and lower positions which spaces are defined by inserting the upper and lower squeeze-plates to the open ends, supplying molding sand through the sand-filling port to the two upper and lower molding spaces, and squeezing the molding sand in the two upper and lower molding spaces.