To improve the strength of a ceramic based building material manufactured particularly by the so called dry method by improving the affinity and sticking property of an aggregate to another matrix such as cement.

In the so called dry method of making a board by supplying a cement compounding material 1 of the ceramic based building material composed of cement, silica, aggregate and a reinforcing fiber and the like on a forming belt 4 with a required additive water in the form of a layer, an aqueous solution prepared by dissolving colloidal silica is used as the water component supplied to the cement compounding material layer 1 on the forming belt 4.