A web film movement compensating device for a web film movement compensation between continuous forward movement section and intermittent forward movement section for an automatic horizontal bag-forming and -filling machine, comprising: first and second guide rollers (1, 2) parallel to one another arranged such that they can rotate freely in stationary positions between a continuous driving device and an intermittent driving device; a first compensation roller parallel to said first and second guide rollers (1, 2) installed such that it can rotate freely on a first pivoting arm oscillating about a pivot shaft parallel to the first and second guide rollers (1, 2); a second compensation roller parallel to the first and second guide rollers (1, 2) installed such that it can rotate freely on a second pivoting arm oscillating about a second pivot shaft parallel to the first and second guide rollers (1, 2) and a movement transmission mechanism transmitting said oscillating movement of the first pivoting arm to the second pivoting arm such that the first and second compensation rollers (3, 4) move closer to one another and to the first and second guide rollers (1, 2) and away from one another and from the first and second guide rollers (1, 2) simultaneously, wherein said first pivot shaft is closer to the first guide roller than to the second guide roller on a first side of a geometric plane containing the axes of the first and second guide rollers (1, 2) and said second pivot shaft is closer to the second guide roller than to the first guide roller on a second side of said geometric plane containing the axes of the first and second guide rollers (1, 2); and wherein a web film, which is moved continuously by said continuous driving device and intermittently by said intermittent driving device, is supported on the first and second guide rollers (1, 2) and on the first and second compensation rollers (3, 4) forming a meander while said first and second pivoting arms (7, 8) perform an oscillating movement between a maximum meander position and a minimum meander position, characterized in that: an elastic element is connected to the first pivoting arm to actuate the first compensation roller in a direction of moving away from the first and second guide rollers (1, 2); and said movement transmission mechanism comprises a first lever arm fixed to the first pivoting arm, a second lever arm fixed to the second pivoting arm, and a connecting rod having a first end connected to said first lever arm by a first articulation and a second end connected to said second lever arm by a second articulation. first and second guide rollers (1, 2) parallel to one another arranged such that they can rotate freely in stationary positions between a continuous driving device and an intermittent driving device; a first compensation roller parallel to said first and second guide rollers (1, 2) installed such that it can rotate freely on a first pivoting arm oscillating about a pivot shaft parallel to the first and second guide rollers (1, 2); a second compensation roller parallel to the first and second guide rollers (1, 2) installed such that it can rotate freely on a second pivoting arm oscillating about a second pivot shaft parallel to the first and second guide rollers (1, 2) and a movement transmission mechanism transmitting said oscillating movement of the first pivoting arm to the second pivoting arm such that the first and second compensation rollers (3, 4) move closer to one another and to the first and second guide rollers (1, 2) and away from one another and from the first and second guide rollers (1, 2) simultaneously, wherein said first pivot shaft is closer to the first guide roller than to the second guide roller on a first side of a geometric plane containing the axes of the first and second guide rollers (1, 2) and said second pivot shaft is closer to the second guide roller than to the first guide roller on a second side of said geometric plane containing the axes of the first and second guide rollers (1, 2); and wherein a web film, which is moved continuously by said continuous driving device and intermittently by said intermittent driving device, is supported on the first and second guide rollers (1, 2) and on the first and second compensation rollers (3, 4) forming a meander while said first and second pivoting arms (7, 8) perform an oscillating movement between a maximum meander position and a minimum meander position, characterized in that: an elastic element is connected to the first pivoting arm to actuate the first compensation roller in a direction of moving away from the first and second guide rollers (1, 2); and said movement transmission mechanism comprises a first lever arm fixed to the first pivoting arm, a second lever arm fixed to the second pivoting arm, and a connecting rod having a first end connected to said first lever arm by a first articulation and a second end connected to said second lever arm by a second articulation. an elastic element is connected to the first pivoting arm to actuate the first compensation roller in a direction of moving away from the first and second guide rollers (1, 2); and said movement transmission mechanism comprises a first lever arm fixed to the first pivoting arm, a second lever arm fixed to the second pivoting arm, and a connecting rod having a first end connected to said first lever arm by a first articulation and a second end connected to said second lever arm by a second articulation.