To obtain a low-cost deflocculant for a slurry excellent in dispersibility and preservability by using a zeolite having monovalent cation releasing ability.

A slurry used in ceramic molding is prepared by using a ceramic material of 0.01-500 μm average particle diameter such as porcelain clay, kaolin feldspar, silica, powder of potsherd, alumina, sericite or talc, a solvent such as water, and a zeolite of 0.01-500 μm average particle diameter having monovalent cation releasing ability as a deflocculant. The amount of the zeolite is 0.01-20 wt.% of the amount of the ceramic material. The concentration of the ceramic material is appropriately about 50-85 wt.%. Since the deflocculant for the slurry releases monovalent cations that contribute to dispersibility in the solvent or adsorbs or ion-exchanges multivalent cations that hinder dispersion while releasing monovalent cations, the ceramic powder is efficiently dispersed in the slurry. The deflocculant is excellent also in work efficiency, and steps after the preparation of the slurry are shortened.