PURPOSE: To provide an impervious resilient membrane for hydropneumatic accumulator with satisfactory impermeability and durability which consists of a resilient membrane such as thermoplastic polyurethane and a gas- impermeable material such as ethylene-vinyl alcohol copolymer buried therein.

CONSTITUTION: (A) A thermoplastic polyurethane, block polyether amide, flexible polyester or a mixture thereof as a first material is mixed with (B) an ethylene- vinyl alcohol copolymer, polyamide, polyvinylidene chloride or a mixture thereof as a second material at a temperature of 150-250°C in a screw within an extruding machine, and formed into a film by extrusion, thereby, an impervious resilient membrane having a structure in which small sections 1 of the gas- impermeable component B are buried in the total body consisting of the elastic membrane M of the component A, which is mounted on a hydropneumatic accumulator in order to receive the gas pressure by one and the liquid pressure by the other is provided.