PURPOSE: To impart gas barrier function to a container and accurately form the flange thereof, by thermally forming a container body with a laminated sheet and molding a flange by an inserting injection method along the upper peripheral edge of the container body.

CONSTITUTION: A plastic container consists of a container body 1 having a bottom 2 and a wall 3 formed integrally and a flange portion 5 having a flange 4 thermally bonded to the upper peripheral edge of the container body and the container is sealed by crimping the flange 4 and a metal lid 6 together. The container body 1 is produced by cutting after thermal formation of a thermoplastic resin sheet 7. If the gas barrier function is required of the container, a laminated sheet formed with a resin excellent in gas barrier function by coextrusion and dry lamination, is used. The cut container body 1 is inserted in a metal injection molding die for only injection molding the flange portion 5. On ejection, a molded flange 4 is obtained and thus an integrally formed container is produced. The bottom and wall of the formed container show the effect of gas barrier as required and also a dimensionally stable flange is formed.