A long obliquely stretched film is obtained having an orientation axis in a direction with an angle ¸s of 45° to 85° from a width direction by grasping both side ends in the width direction of a longitudinally stretched film with an average retardation Re 1 by grasping means; stretching the film under a condition that a long obliquely stretched film sample with an average retardation Re 2 (Re 2 is smaller than Re 1 ) can be obtained and traveling speeds of the grasping means are substantially equal at the film both side ends through a preheating zone, a stretching zone and a fixing zone; releasing the both side ends of the film from the grasping means; and taking it up around a winding core.
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