PURPOSE: To insert a film in a ring at the time of molding to obviate the need for securing them by heat sealing by a method wherein a molded material is removed by opening molds after a charged material is cooled and set.

CONSTITUTION: A very thin synthetic resin film 8 is tensed between a mold 3 and the other mold 5. After the film 8 is tensed, the molds 3, 5 are brought into a closed state. The film 8 is shaped into a bag form by bag-form shaping female and male mold parts 7, 6. The film 8 is clamped by peripheral parts 9, 10 of one half-face molding cavity 2 and the other half-face molding cavity 4. In the clamped state, a hot melt synthetic resin 12 is injected to be charged in the half-face molding cavity 2 through a gate 11 provided in the mold 3. A tear part 13 is formed by tearing a part of the film 8 by the injection pressure and temperature. The hot melt synthetic resin 12 is continuously charged also in the half-face molding cavity 4 through the teared part 13. After the charged material is cooled and set, the molds are opened, and a molded material 15 is removed. A finished article is obtained by finishing the molded material 15, e.g. cutting an excess part 16.