A fibrous body manufacturing method includes: a first supplying step of supplying a first raw material containing a first fiber group; a second supplying step of supplying a second raw material containing a second fiber group and a binder, the second fiber group having a length-average fiber length not less than a length-average fiber length of the first fiber group, the binder being configured to bond fibers together; a forming step of forming a first deposited material by depositing a first mixed material containing the first raw material and the second raw material; and a bonding step of bonding first fibers of the first fiber group and second fibers of the second fiber group that are contained in the first deposited material together using the binder to form a first fibrous body.