To provide a plastic substrate causing no drop of its electrical conductivity even if formed an oriented film and causing no white spot trouble even if incorporated in an image display device, and to provide a method for producing the plastic substrate.

The method for producing the plastic substrate having a coefficient of thermal expansion of ≤50 ppm/°C, a breaking elongation of 3-50% and a heat distortion temperature of ≥200°C comprises compounding a metal oxide in a polymer followed by conducting film formation, and carrying out a heat treatment of the resultant film at a temperature higher than the Tg of the polymer followed by another heat treatment at a temperature not lower than 50°C but lower than the Tg of the polymer for 3-200 h while applying tension of ≤20 kg/m onto the substrate.