A device for stretching a thermoplastic film simultaneously in the longitudinal direction and the transverse direction, comprising, on each side of the film to be stretched, - grasping members for grasping a lateral edge of the film, in particular in the form of clamps; - a first guide rail, close to the film, on which these grasping members are placed and along which these grasping members are able to move; - guide members; - a second guide rail, on which these guide members are placed and along which these guide members are able to move; this second rail is rigidly connected to said first rail, in that its position is not adjustable relative to this first rail in a direction transverse to the film; and - first connecting rods connecting the grasping members and the guide members, the first connecting rods being movable relative to these grasping members and these guide members along first axes; Characterized in that, on each side of the film, - each guide member is connected to a single grasping member by one or several of said first connecting rods, and is connected to a first longitudinal adjusting member (10; 30) by one or several second connecting rods, this or these second connecting rods being movable relative to the guide member and relative to this first longitudinal adjusting member (10; 30) along second axes parallel to said first axes; said second connecting rod(s) of a first guide member and said second connecting rod(s) of a second guide member consecutive to said first guide member are connected to said first longitudinal adjusting member (10; 30) at pivot points that are combined or close on this first longitudinal adjusting member (10; 30); and - the device includes adjusting means (20, 21, 22) for adjusting the position and orientation of said first longitudinal adjusting member (10; 30) relative to said first and second guide rails (R1, R2). - grasping members for grasping a lateral edge of the film, in particular in the form of clamps; - a first guide rail, close to the film, on which these grasping members are placed and along which these grasping members are able to move; - guide members; - a second guide rail, on which these guide members are placed and along which these guide members are able to move; this second rail is rigidly connected to said first rail, in that its position is not adjustable relative to this first rail in a direction transverse to the film; and - first connecting rods connecting the grasping members and the guide members, the first connecting rods being movable relative to these grasping members and these guide members along first axes; - each guide member is connected to a single grasping member by one or several of said first connecting rods, and is connected to a first longitudinal adjusting member (10; 30) by one or several second connecting rods, this or these second connecting rods being movable relative to the guide member and relative to this first longitudinal adjusting member (10; 30) along second axes parallel to said first axes; said second connecting rod(s) of a first guide member and said second connecting rod(s) of a second guide member consecutive to said first guide member are connected to said first longitudinal adjusting member (10; 30) at pivot points that are combined or close on this first longitudinal adjusting member (10; 30); and - the device includes adjusting means (20, 21, 22) for adjusting the position and orientation of said first longitudinal adjusting member (10; 30) relative to said first and second guide rails (R1, R2).