To manufacture an excellent film having no line-like defect on its surface by means of a molten extrusion method.

A film is manufactured by melting and extruding a thermoplastic resin by use of an extruder and a die wherein surface roughness Ry of a connecting pipe portion from the outlet of the extruder to the die is not more than 1.0S, surface roughness Ry of a die lip portion is not more than 0.5S, surface roughness Ry of the flow portion of the die is not more than 0.6S, surface roughness Ry of a die manifold portion is not more than 0.7S and surface roughness Ry of a die supply portion is not more than 0.8S respectively.