An ultrasonic welding apparatus that performs an ultrasonic welding process to a sheet-like member, the sheet-like member being associated with an absorbent article, the sheet-like member being transported while being wound onto an outer circumferential face of a rotating member, the rotating member rotating about its central axis, the apparatus comprising: the rotating member; an ultrasonic processing unit that rotates about the central axis together with the rotating member, and that includes as ultrasonic processing members a horn that vibrates ultrasonically and an anvil between which and the horn the sheet-like member is sandwiched; and the horn and the anvil being guided so as to reciprocate in a CD direction, the CD direction intersecting a transport direction of the sheet-like member, the horn and the anvil reciprocating in the CD direction with respect to a part (lap) of the sheet-like member, the part being wound around the rotating member, characterized in that both of the horn and the anvil are in contact with the sheet-like member in a predetermined section during movement in both of a forward path and a return path of the reciprocation, with both of the horn and the anvil reciprocating in the CD direction while the sheet-like member is sandwiched between the horn and the anvil, the predetermined section being included in the outer circumferential face of the rotating member and extending in the CD direction, in both of the forward path and the return path, the horn vibrates ultrasonically when the ultrasonic processing member is passing the predetermined section, the apparatus further comprising an ultrasonic-energy regulating unit, the ultrasonic-energy regulating unit making an amount (J/m) of applied ultrasonic energy per unit length in the CD direction of the predetermined section of the forward path different from an amount (J/m) of applied ultrasonic energy per unit length in the CD direction of the predetermined section of the return path. the rotating member; an ultrasonic processing unit that rotates about the central axis together with the rotating member, and that includes as ultrasonic processing members a horn that vibrates ultrasonically and an anvil between which and the horn the sheet-like member is sandwiched; and the horn and the anvil being guided so as to reciprocate in a CD direction, the CD direction intersecting a transport direction of the sheet-like member, the horn and the anvil reciprocating in the CD direction with respect to a part (lap) of the sheet-like member, the part being wound around the rotating member, characterized in that both of the horn and the anvil are in contact with the sheet-like member in a predetermined section during movement in both of a forward path and a return path of the reciprocation, with both of the horn and the anvil reciprocating in the CD direction while the sheet-like member is sandwiched between the horn and the anvil, the predetermined section being included in the outer circumferential face of the rotating member and extending in the CD direction, in both of the forward path and the return path, the horn vibrates ultrasonically when the ultrasonic processing member is passing the predetermined section, the apparatus further comprising an ultrasonic-energy regulating unit, the ultrasonic-energy regulating unit making an amount (J/m) of applied ultrasonic energy per unit length in the CD direction of the predetermined section of the forward path different from an amount (J/m) of applied ultrasonic energy per unit length in the CD direction of the predetermined section of the return path. that rotates about the central axis together with the rotating member, and that includes as ultrasonic processing members a horn that vibrates ultrasonically and an anvil between which and the horn the sheet-like member is sandwiched; and a horn that vibrates ultrasonically and an anvil between which and the horn the sheet-like member is sandwiched; and the horn and the anvil being guided so as to reciprocate in a CD direction, the CD direction intersecting a transport direction of the sheet-like member, the horn and the anvil reciprocating in the CD direction with respect to a part (lap) of the sheet-like member, the part being wound around the rotating member, characterized in that both of the horn and the anvil are in contact with the sheet-like member in a predetermined section during movement in both of a forward path and a return path of the reciprocation, with both of the horn and the anvil reciprocating in the CD direction while the sheet-like member is sandwiched between the horn and the anvil, the predetermined section being included in the outer circumferential face of the rotating member and extending in the CD direction, in both of the forward path and the return path, the horn vibrates ultrasonically when the ultrasonic processing member is passing the predetermined section, the apparatus further comprising an ultrasonic-energy regulating unit, the ultrasonic-energy regulating unit making an amount (J/m) of applied ultrasonic energy per unit length in the CD direction of the predetermined section of the forward path different from an amount (J/m) of applied ultrasonic energy per unit length in the CD direction of the predetermined section of the return path.