To provide a working apparatus for sheets having good welding and finish of welding and fusion cutting.

The working apparatus for sheets is composed of a horn 2 and receiving plate 3 having an edge 1 in any one of opposite faces and reciprocation device 4 for permitting at least one of the horn 2 and receiving plate 3 to move forward and rearward, and to press-hold an interposed sheet A between the horn 2 and the receiving plate to be welded or welded and fusion-cut through a supersonic vibration transmission from the horn 2 under a press- holding condition, in which between the horn 2 having no edge 1 or the receiving plate and sheet, a pliable plate body 21 is interposed which does not preclude the passage of supersonic waves with respect to the welding or welding and fusing apparatus, thus making a touch of the edge uniform evenly.