An amylase inhibitor consisting essentially of a protein constructed of 248 amino acid residues having two subunits, each identified as SEQ ID NO:1, in which a single band is observed at a mobility of 0.26 by polyacrylamide gel electrophoresis. The amylase inhibitor can be extracted from wheat and purified by absorption on a cation exchange resin. It is useful for inhibiting an increase in blood glucose level, controlling insulin secretion, suppressing appetite, and as a food additive. The new amylase inhibitor can be used in combination with a protein composed of two subunits, each identified as SEQ ID NO:2, the total content of both proteins being not less than 20% by weight.