A web adhesive application device, adhesive application method, and the cardboard sheet manufacturing device are provided with: an adhesive liquid tank for storing an adhesive liquid; an adhesive application roll is configured for transferring the adhesive liquid to an adhesive application region adjusted according to a paper width of a bottom liner board to be glued together with a single face cardboard sheet; a doctor roller for adjusting the adhesive liquid to a set film thickness; scraping members in pressured contact with the surface of the adhesive application roll on the upstream side of the nip section with the doctor roller; and damming members in contact with the surface of the adhesive application roll on the upstream side of the nip section with the doctor roller in the rotation direction and on the downstream side of the scraping member contact positions in the rotation direction.