PURPOSE: To obtain a molding method for a shaping balloon of thermoplastic resin which is simple and capable of controlling thickness, by a method wherein the resin is dissolved into a solvent having a plasticizing effect to the thermoplastic resin, coating is formed on a male mold and the outer skin is released from the male mold under a state wherein the solvent is contained more than a specific rate.

CONSTITUTION: As thermoplastic resin, vinyl chloride resin or styrene resin or ethylene resin representing the value of the modulus of elasticity of more than 200kg/cm2 is used, and as a solvent representing a plasticizing effect, for example, THF or MEK is appropriate for the vinyl chloride resin. After the resin has been dissolved into a solvent and viscosity of the same has been prepared beforehand, a male mold for a shaping balloon is immersed in the solution or a resinous solution is blown against the external surface of the male mold. In a range wherein the resin does not represent adhesion but represent a high elongation in a sphere of the low modulus of elasticity, for example, in case of application of the THF, which is the vinyl chloride resin, as the solvent, the same is released from the mold by drying the same up to solvent content of more than 5% and less than 20%. The shaping balloon released from the mold is restored to the original form when the same is heated at the temperature of more than the glass transition temperature.