PURPOSE: To obtain a ceramic sintered body having superior mechanical strength by kneading ceramic powder and a sintering aid with the NH3 salt of smectite as a binder and carrying out spray drying, granulation, molding and sintering in a nitrogen atmosphere.

CONSTITUTION: Ceramic powder such as silicon nitride powder as the base material of a sintered body and a sintering aid such as Y2O3 or Al2O3 are kneaded with smectite contg. ammonium ion substd. for metal cation, e.g. saponite or montmorillonite as a binder. The kneaded material is spray-dried, granulated and molded and this molded body is sintered by heating in a nitrogen atmosphere to obtain a ceramic sintered body. Since the ammonium salt of smectite as an inorg. high molecular compd. not evaporating even at a high temp. is used as the binder, the internal structure of the sintered body is made dense and a high strength sintered body can be produced.