Provided is an ultrasonic welding device which carries out an ultrasonic weld process on a sheet-shaped member which is conveyed while being wound around the outer circumference face of a rotating member which rotates about a central axis. The ultrasonic welding device comprises the rotating member, and an ultrasonic processing unit which rotates about the central axis together with the rotating member. The ultrasonic processing unit further comprises a hone which ultrasound oscillates, and an anvil which sandwiches the sheet-shaped member together with the hone. At least one of the ultrasonic processing members, that is, the hone and/or the anvil, is guided to be capable of reciprocal movement in a CD direction which intersects the direction of the conveyance of the sheet-shaped member, and the ultrasonic processing member carries out reciprocal movement in the CD direction with respect to a portion of the sheet-shaped member which is wound about the rotating member. In the reciprocal movement, the ultrasonic processing member moves to locations in the CD direction upon the sheet-shaped member which are beyond each end part thereof, and the hone and the anvil face one another even in the said locations therebeyond. The outer circumference face of the rotating member further comprises each zone whereupon each end part of the sheet-shaped member is to be located. With the zone among each of the zones which the ultrasonic processing member passes through when starting to cut across the sheet-shaped member in the CD direction designated a first zone, and the zone which the ultrasonic processing member passes through when finishing cutting thereacross designated a second zone, the ultrasonic welding device further comprises an ultrasonic energy adjustment unit which starts reducing the amount of ultrasonic energy (J/m) which is inputted per unit length in the CD direction when the ultrasonic processing member passes through the second zone.L'invention concerne un dispos
