A method for manufacturing watermarked paper, comprising: a step of forming a first fibrous panel which comprises at least one watermark element; a step of forming a second, thin fibrous panel; a step of removal, by way of suction, of at least one portion of the second, thin fibrous panel in order to produce a localized reduction in thickness at a first face of the second, thin fibrous panel, so as to provide at least one accommodation seat intended to accommodate a security element; a step of coupling between the first fibrous panel and the face of the second, thin fibrous panel which lies opposite the first face.

Disclosed is a sheet manufacturing apparatus including a rotatable drum unit in which a plurality of openings are formed; a web forming unit that forms a web by using a material containing fibers passing through the openings; a housing unit that covers at least a portion of the drum unit in which the openings are formed; a material supply port that is provided to supply the material in a direction along a rotational axis of the drum unit to the inside of the drum unit by airflow; and an air intake port that is provided to supply air that does not contain the material in the direction along the rotational axis of the drum unit to the inside of the drum unit. The web forming unit includes a mesh belt on which the material is deposited and a suction unit that sucks the material onto the mesh belt.