A sheet manufacturing apparatus includes a defibrating unit configured to defibrate a stock material including fibers, a screening unit configured to allow a defibrated material that has been defibrated at the defibrating unit to pass through a plurality of openings, and a forming unit configured to form a sheet by using a passed material that has passed through the openings. The screening unit has a sieve unit having the openings, and a transferring unit that is located below the sieve unit and with which the cross-sectional area of an internal space in a horizontal direction decreases going downward.