A method for manufacturing a composite sheet (20) of an absorbent article (1) to manufacture a composite sheet (20) including a first continuous sheet (21), a second continuous sheet (22), and an elastic string (23) to be arranged between the first continuous sheet (21) and the second continuous sheet (22), the method includes: transporting the first continuous sheet (21), the second continuous sheet (22), and the elastic string (23), in a state where the elastic string (23) arranged between the first continuous sheet (21) and the second continuous sheet (22) is at least partially interposed between first protruding parts (251) and second protruding parts (252), by causing a first rotation body (25) to rotate, the first rotation body (25) including the first protruding parts (251) and the second protruding parts (252) protruding radially outwardly； and performing processing to the first continuous sheet (21) and the second continuous sheet (22) by sandwiching the first continuous sheet (21) and the second continuous sheet (22) between a second rotation body (26) and the first protruding parts (251) and the second protruding parts (252), during transporting with the first rotation body (25).
