A method for producing a disposable worn article in which a welding target component having facing portions is continuously welded with a predetermined pattern in a range from one end portion to the other end portion of the facing portions, the facing portions being two mutually-facing portions constituted by thermoplastic sheets, the method comprising: a rotating step of rotating an anvil about a predetermined rotating shaft, the anvil having a welding surface for continuously welding the facing portions to each other with the predetermined pattern between the welding surface and a horn for applying ultrasonic vibrations to the facing portions; and a welding step of intermittently supplying, in a state in which the anvil is rotated, a plurality of the welding target components to a place between the welding surface of the anvil and the horn to continuously weld the facing portions to each other with the predetermined pattern in each of the welding target components, wherein a step of providing the welding surface of the anvil over a whole circumference about the rotating shaft such that a clearance between the welding surface of the anvil and the horn is maintained at a clearance at which the facing portions are continuously weldable to each other with the predetermined pattern regardless of a rotating position of the anvil in the rotating step, the horn has an oscillating surface that applies ultrasonic vibrations to the facing portions and extends in a tangential direction to the welding surface of the anvil, and the method for producing the worn article further comprises an adjustment step of adjusting, when a portion of the oscillating surface facing the welding surface of the anvil is degraded, a mounting position of the horn with respect to a mounting section on which the horn is mounted such that a portion other than the degraded portion of the oscillating surface faces the anvil. a rotating step of rotating an anvil about a predetermined rotating shaft, the anvil having a welding surface for continuously welding the facing portions to each other with the predetermined pattern between the welding surface and a horn for applying ultrasonic vibrations to the facing portions; and a welding step of intermittently supplying, in a state in which the anvil is rotated, a plurality of the welding target components to a place between the welding surface of the anvil and the horn to continuously weld the facing portions to each other with the predetermined pattern in each of the welding target components, wherein a step of providing the welding surface of the anvil over a whole circumference about the rotating shaft such that a clearance between the welding surface of the anvil and the horn is maintained at a clearance at which the facing portions are continuously weldable to each other with the predetermined pattern regardless of a rotating position of the anvil in the rotating step, the horn has an oscillating surface that applies ultrasonic vibrations to the facing portions and extends in a tangential direction to the welding surface of the anvil, and the method for producing the worn article further comprises an adjustment step of adjusting, when a portion of the oscillating surface facing the welding surface of the anvil is degraded, a mounting position of the horn with respect to a mounting section on which the horn is mounted such that a portion other than the degraded portion of the oscillating surface faces the anvil.