To obtain a binder for molding ceramics, enabling to obtain a green sand molded product having proper flexibility and sufficient strength by polymerizing an N-vinyl carboxylic acid amide having a specific structure.

This binder for molding ceramics comprises a (co)polymer having a weight-average mol.wt. of 100,000-5,000,000 and obtained by (co) polymerizing an N-vinyl carboxylic acid amide of the formula (R1, R2 are each H or methyl), if necessary, with a copolymerizable other monomer in the presence of 5×10-4-5 wt.%, preferably 10-3-2 wt.%, of an azobis initiator such as azobisisobutyronitrile or azobis(2-amidinopropane) dihydrochloride at 0-80°C for 0.5-30 hr. 100 pts.wt. of a body for potteries, such as feldspar, silica, potter's clay, kaolin or clay, or a body for ceramics, such as alumina, zirconia, ferrite, silica, beryllia or magnesia, is mixed with 0.1-25 pts.wt., preferably 0.2-20 pts.wt., of the binder for molding the ceramics to obtain a composition for molding ceramics.