A flexible electronic device excellent in heat liberation characteristics and toughness and a production method for actualizing thereof in low cost and with satisfactory reproducibility are provided. A protection film is adhered onto the surface of a substrate on which surface a thin film device is formed. Successively, the substrate is soaked in an etching solution to be etched from the back surface thereof so as for the residual thickness of the substrate to fall within the range larger than 0 μm and not larger than 200 μm. Then, a flexible film is adhered onto the etched surface of the substrate, and thereafter the protection film is peeled to produce a flexible electronic device.