An object of the present invention is to provide a process for producing fiberous board with which fiberous board exhibiting high bending strength and high stiffness at a wide range of heating temperatures and a wide range of compressing and heating times. In the present invention, fiberous board having an initial flexural modulus of at least 300 MPa in three point bending test is obtained by forming a web by correcting sheath-core composite fibers of which a core component is formed from a copolymer of ethylene glycol and terephthalic acid and the sheath component is formed from ethylene glycol, adipic acid, terephthalic acid, isophthalic acid; and/or diethylene glycol. The web is then compressed in a direction of thickness and heated, so that the sheath component softens and melts and the sheath-core composite fibers are melt bonded together and molded into a flat plate shape.