A container having a plurality of orifices in an outer peripheral wall and having a space communicating with the orifices is rotated to extrude an electrically charged raw material liquid containing a polymer material from the space through the orifices by centrifugal force. This allows the electrically charged raw material liquid to form a fibrous material. At this time, the raw material liquid is supplied to the space in which the raw material liquid is filled by a raw material liquid pump so that the raw material liquid is extruded from the orifices at a predetermined pressure. That is, the raw material liquid in the space is pressurized. Also, the shape of the space in the container is set so that the centrifugal force exerted on the raw material liquid is constant.