To provide an apparatus for readily producing a mat of composite fiber body so as to have a density gradient in the thickness direction in a mat such as an SL (Synthetic fiber Lock) plate having a high space ratio.

The apparatus for producing a composite fiber body comprises a supply means 1 for mixing a natural fiber raw material with a chemical fiber raw material and supplying the mixture to the air transportation means, the air transportation means 2 for grinding these raw materials into fine fibers and blowing off these fibers, a transportation means 3 for receiving these blown fibers in a laminar state and transporting the fibers and a binder means 4a for bonding the transported laminar fiber raw material layer 5.