To remarkably improve properties such as the strength of a film, internal stress relaxation and impact resistance by interposing one more specific layer between two thermoplastic resin sheet-like films, to obtain a double-layered sheet-like film and using a specific member, to fuse the film and splice both end parts.

One layer is interposed between two thermoplastic resin sheet- like films by using a kind of rubber, elastomer or inorganic thin film having a functional adhesive existing on the surface, to form the double-layered sheet- like film 4. This film 4 is wound on a columnar member 1 and the member 1 is inserted into a tubular member 2, in a state where winding top and bottom ends are overlapped. Then, the whole is maintained in a heated state for a specified time, to fuse the film in the overlapped part and splice both end parts of the film. In a tubular film obtained by this method, the uniformity of film thickness accuracy is ±5 μm and materiality such as an elastic modulus and the impact resistance is improved.