To make an appearance also excellent while strength is improved by a method wherein a raw material is sent through a blower prior to scattering the raw material.

A specific amount of a raw material stored in a storing tank is taken out from the storing tank, and delivered to a mat forming device 7. At its previous stage the raw material is sent through a blower 2, and a wood fiber flock contained in the raw material R is loosened by a cutting effect of a fan of the blower 2 and its blast blowing effect. Then, the wood fiber and a synthetic resin binder are homogeneously mixed. The raw material R treated by such the loosening is scattered on a net conveyor 4 as a support means inside the scattering tower 3 of the mat forming device 7, and formed in a mat M. Then, after adjusting a thickness of the mat with a blade 5, the mat is preliminarily pressed with a belt conveyor type preliminary pressing machine 6, and further hot pressed with a belt conveyor type main pressing machine 7.