To enable a continuous decomposition treatment with enzyme, by disconnecting fiber waste consisting of composite stock of synthetic fibers and natural fibers to an approximately specified width, then joining the cut fiber waste by sewing, adhering, or the like, to form a continuous long-sized belt-like body and supplying this body to a decomposition treating device for performing enzyme treatment with an enzyme treating liquid.

The fiber waste 1 consisting of the composite stock of the synthetic fibers and the natural fibers is disconnected to an approximately specified width and the cut fiber waste is joined by sewing, adhering, or the like, to form the continuous long-sized belt-like body, by which the long-sized belt-like body 2 of the fiber waste is obtained. The long-sized belt-like body 2 is supplied by plural arrays of guide rollers 3 to a treating vessel 4 in which the enzyme treating liquid is housed and is subjected to the enzyme treatment. Further, the long-sized belt-like body 2 is thereafter supplied to a drive guide section 5 by a conveyor and the enzyme treating liquid is shower sprayed from nozzles 6 installed in plural arrays above the drive guide section 5. The shower sprayed enzyme treating liquid is passed through the long-sized belt-like body 2 and, thereafter, the enzyme treating liquid is collected in a receiving tray 7 and is sent to a treating vessel through a connecting pipe 8.