To adjust operating ranges of both sealing bodies while keeping the meshing position of the both sealing bodies.

A sealing device for a bag making and filling machine includes: a supporting body 33 supported by a support frame 10 such that the movement thereof is adjustable, the support frame supporting the both sealing bodies 8 and 9 movably; operation bodies 36 rotatably supported by the supporting body 33; guiding bodies 38 movably supported by the operation bodies 36, and rotatable together with the operation bodies 36; movable units 22 and 39 rotatably supported by the guiding bodies 38 at an eccentric position relative to the operation bodies 36; a cooperation mechanism for moving the both sealing bodies 8 and 9 in association with the rotation of the movable unit 22 by the rotation of the operation bodies 36; a rotating body coupled to the guiding bodies 38, and rotatably supported by the supporting body 33 while being concentric with the operation body 36; and a changing unit for varying the phase of the rotating body relative to the operation bodies 36 according to change in the supporting position of the supporting body 33 so as to move the eccentric position of the movable unit 22 on a line extending through the rotational center of the operation body 36.