PURPOSE: To easily obtain a thick resin reinforced fiber board having uniform adhesion strength by such an arrangement wherein a specific fiber board is coated and impregnated with thermosetting type synthetic resin, and plural sheets of this fiber board are laminated and the whole boards are integrated together by heating and pressurizing them.

CONSTITUTION: At first, one side or both sides of a wooden or mineral fiber board 1 is coated and impregnated with thermosetting type synthetic resin liquid such as melamine resin solution, etc. by a spray, etc. And, plural sheets of this fiber board 1 are laminated with their resin impregnated surfaces brought to contact face to face and then this laminated fiber board 3 is heated anc compressed by a press 4 and impregnated resin liquid is caused to penetrate throughout the fiber board and harden, and the titled resin reinforced fiber board is obtained by integrating the whole board. It is preferable that different nature is given to the surface layer portion and internal layer portion of a laminated fiber board by changing the kind of resin liquid to be coated and impregnated in each side of a fiber board.