board tt c is dependent on the fiber weight fraction u03b1 by weight and the total transmittance of matrix resin tt m and a sufficient see through property can be exhibited when the following conditions are satisfied as has been mentioned above when total transmittance of the fiber reinforced resin does not satisfy the above conditions the total transmittance markedly decreases as the fiber weight fraction increases as a result of which no sufficient see through property can be achieved when such a fiber reinforced resin is made into a concrete form having a necessary strength the thermoplastic resin used as a base material for the concrete form of the invention is not critical so far as the resin has a strength enough to be usable as a concrete form thermoplastic resins such as polyethylene polypropylene abs resin vinyl chloride resin pmma nylon polycarbonate resin and the like can be used for this purpose among these resins polypropylene is preferred from the viewpoint of heat resistance strength and economy as the reinforcing fiber glass fiber is preferred though other fibers such as alumina fiber and the like are also usable without limitation the fiber weight fraction may be any value so long as it is in the range defined above from the viewpoint of strength and economy however the fiber weight fraction is usually from 10 to 50 by weight and preferably from 15 to 30 by weight when glass fiber is used the fiber length is usually from 0 1 to 50 mm and preferably from 1 to 15 mm.