NOVELTY - Manufacture of biaxially stretched film involves preheating a thermoplastic resin film to a temperature in an elastomeric flat region of a storage modulus curve, biaxially stretching the thermoplastic resin film at stretch speed of 500%/minute or more while heating the thermoplastic resin film to a temperature in the elastomeric flat region, cooling the thermoplastic resin film at temperature in a glass-rubber transition region or a glass region of the storage modulus curve, and relaxing the thermoplastic resin film at a temperature in the glass-rubber transition region.    USE - Manufacture of biaxially stretched film used for polarizer protective film, decoration film and multilayer film (all claimed). Uses include but are not limited to liquid-crystal guard plate, surface material of portable information terminal, display window protective film, light guide film, front plate of display, infrared rays cut film, shatter-resistant window film, scattering prevention film, decoration film, back sheet of solar cell, etc.    ADVANTAGE - The method enables manufacture of biaxially stretched film having minimal heat shrinkage and excellent dimensional stability.    DETAILED DESCRIPTION - Manufacture of biaxially stretched film involves preheating a thermoplastic resin film to a temperature in an elastomeric flat region of a storage modulus curve, biaxially stretching the thermoplastic resin film at stretch speed of 500%/minute or more while heating the thermoplastic resin film to a temperature in the elastomeric flat region, cooling the thermoplastic resin film at temperature in a glass-rubber transition region or a glass region of the storage modulus curve, and relaxing the thermoplastic resin film at a temperature in the glass-rubber transition region. The unstretched thermoplastic resin film comprises thermoplastic resin layer which is biaxially stretched in a longitudinal direction and a width direction, and biaxially stretched film. An INDEPENDENT CLAIM is included for multilayer film, which has laminated structure of biaxially stretched film, and other resin film.