Abstract: A method and apparatus for stretching a thermoplastic polymer film in which the opposite selvages of the film are gripped by gripping means and are stretched transversely during heating by moving the selvages along two divergent arcuate paths lying in the same plane and extending over a predetermined circumferential range from a quater to a half of the full circumference of the circle containing the arcuate paths. In order to avoid drawbacks in the existing equipment such as irregular molecular orientation in and rupture of the film, the longitudinal travel of the film while being stretched is controlled by controlling means so that the central web portion is advanced by substantially the same distance as the gripped film selvages, whereby the amound of longitudinal movement of the film is held always constant throughout the width of the film.