The objective of this study is to evaluate the suppressive effect of buckwheat-albumin hydrolysate on postprandial?hyperglycemia?and identify the peptide responsible to the function. Buckwheat-albumin hydrolysate was prepared by using?digestive enzymes?and was orally administered to rats together with soluble starch. The blood was taken from the tail vein up to 90 min after?oral administration?to measure blood-glucose and plasma-insulin levels. The peptide with?α-amylase inhibitory activity was purified from the buckwheat-hydrolysate by gel-filtration chromatography,?α-amylase?affinity chromatography, and?high performance liquid chromatography?(HPLC). The amino-acid sequence of the peptide was identified by a protein sequencer and was compared with that in the buckwheat-genome database. Buckwheat-albumin hydrolysate significantly suppressed the elevation of?blood glucose?level 15 min after starch administration. The amino-acid sequence of the peptide with?α-amylase inhibitory activity was YVEPDCGNLGCCYHC in the parental protein of molecular mass 17.8 kDa and theoretical pI?4.77. The amino-acid sequence, molecular weight, and pI?of the parental protein in buckwheat?albumin?were different from those of?α-amylase inhibitor in wheat albumin. This study suggests that the novel?α-amylase inhibitor identified in buckwheat albumin is a potential candidate for a functional food material to suppress postprandial blood glucose elevation.