To reutilize FRP waste by using the ground matter of the FRP waste as a filler of a resin concrete layer being the reinforcing layer of an FRP molded product.

The ground matter of FRP waste is used as the filler of a resin concrete layer 2 being the reinforcing layer of an FRP molded product. At first, the FRP waste is crushed by a grinder and roughly crushed by a twin- screw shearing machine. Next, this crushed matter is ground by a hammer breaker. In the resin concrete layer 2 being the reinforcing layer 2, about 100-150 wt.% of the ground matter of the FRP waste is compounded with about 100 wt.% of the total amt. of an unsaturated polyester resin and a low shrinkage agent resin. The ground matter of the FRP waste is classified into some groups according to a particle size and the classified matters are mixed so that the mixing ratio at every classification becomes a predetermined mixing ratio to be used as a filler. By this constitution, the FRP waste can be reutilized and the reutilization of resources can be realized.