To obtain a soluble polymer film having necessary gas-tightness and/or moisture-proofness, enabling relatively easy operation for holding a substance susceptible to air and/or moisture and charging into a chemical reactor, easily producible at a reduced cost and soluble in an organic solvent at 20-60°C without generating substances harmful to health in the dissolution process.

This soluble polymer film is composed of (A) 30-99.5wt.% of a thermoplastic polymer consisting of a styrene-butadiene copolymer having a bonded styrene content of 60-85wt.% and a tensile elastic modulus of 1,100-1,800Mpa and (B) 0.5-70wt.% of a thermoplastic rubber consisting of a styrene-butadiene copolymer having a bonded styrene content of 25-35wt.% and a tensile elastic modulus of 2.6-3.5Mpa.