An ultrasonic welding apparatus that performs ultrasonic welding to a sheet-like member 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; and 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 that sandwiches the sheet-like member with the horn; at least either one ultrasonic processing member of the horn and the anvil being guided so as to be able to reciprocate in a CD direction, the CD direction intersecting a transport direction of the sheet-like member, the at least either one ultrasonic processing member of the horn and the anvil reciprocating in the CD direction with respect to a part of the sheet-like member, the part being wound around the rotating member, in the reciprocation, the at least either one ultrasonic processing member of the horn and the anvil moving to a crossed-over position (Pf, Pb) that is located beyond an end part (1aef, 1aeb) of the sheet-like member in the CD direction, the horn and the anvil facing each other at the crossed-over position, the outer circumferential face of the rotating member including sections in which each end part of the sheet-like member is to be positioned, characterized in that the apparatus further comprises an ultrasonic-energy regulating unit, and in the case where, of the sections, a section that the at least either one ultrasonic processing member of the horn and the anvil passes when starting to cross the sheet-like member in the CD direction being a first section (A1aeb), a section that the at least either one ultrasonic processing member of the horn and the anvil passes when finishing the crossing being a second section (A1aef), the ultrasonic-energy regulating unit causing an amount (J/m) of ultrasonic energy to be applied per unit length in the CD direction to start decreasing, when the ultrasonic processing member is passing the second section (A1aef). the rotating member; and 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 that sandwiches the sheet-like member with the horn; 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 that sandwiches the sheet-like member with the horn; a horn that vibrates ultrasonically and an anvil that sandwiches the sheet-like member with the horn; at least either one ultrasonic processing member of the horn and the anvil being guided so as to be able to reciprocate in a CD direction, the CD direction intersecting a transport direction of the sheet-like member, the at least either one ultrasonic processing member of the horn and the anvil reciprocating in the CD direction with respect to a part of the sheet-like member, the part being wound around the rotating member, in the reciprocation, the at least either one ultrasonic processing member of the horn and the anvil moving to a crossed-over position (Pf, Pb) that is located beyond an end part (1aef, 1aeb) of the sheet-like member in the CD direction, the horn and the anvil facing each other at the crossed-over position, the outer circumferential face of the rotating member including sections in which each end part of the sheet-like member is to be positioned, characterized in that the apparatus further comprises an ultrasonic-energy regulating unit, and in the case where, of the sections, a section that the at least either one ultrasonic processing member of the horn and the anvil passes when starting to cross the sheet-like member in the CD direction being a first section (A1aeb), a section that the at least either one ultrasonic processing member of the horn and the anvil passes when finishing the crossing being a second section (A1aef), the ultrasonic-energy regulating unit causing an amount (J/m) of ultrasonic energy to be applied per unit length in the CD direction to start decreasing, when the ultrasonic processing member is passing the second section (A1aef).