<p>This method for producing a long stretched film at least involves a film formation step for forming a long film formed from a thermoplastic resin, an oblique stretching step for obliquely stretching the long film, and a winding step for winding the long stretched film after the oblique stretching step, wherein: an oblique stretching device is provided with gripping tool travel support tools on both sides of the travelling long film; the gripping tool travel support tools are each provided with multiple gripping tools; the gripping tool travel support tools disposed on both sides of the long film have the same number of gripping tools; and the combination of the gripping tools constituting a pair of gripping tools is always the same at a grip start point where the long film is gripped by means of the gripping tools. With said method for producing a long stretched film, it is possible to produce a long stretched film having a small variation in the orientation angles in the width direction.</p>
