PURPOSE: To carry out the uniformization of orientation certainly and easily, by a method wherein a base material to be oriented is transversely oriented along a downwardly widened circular arc track in a heating region by both orienting discs and, after the oriented base material is further transversely oriented in an upwardly widened form, the transversely oriented base material is transferred to an orientation uniformizing disc to be sent in a constant width.

CONSTITUTION: A base material F0 to be oriented is sent into a heating chamber 2 by sending nip rolls 5 and supplied between both orienting discs 1, 1' in such a state that both side flange parts thereof are advanced along the grasping surfaces 1b of said each discs 1, 1'. In the next step, within ranges of almost semi-circular peripheries of the lower half sides of both orienting discs 1, 1', the base material F0 to be oriented is transferred in such a state that the both side flange parts thereof are grapsed to be transversely oriented in a downwardly widened form and further transversely oriented in an upwardly widened form while turned inside out from the lowermost points of said discs 1, 1'. Succeedingly, the oriented film F is sent in a constant width while side flange parts F1 of the film F is turn inside out toward the side of orientation uniformizing discs 2, 2'. By this method, the uniformization of orientation can be carried out certainly and easily.