Dry solid matter (rutin content: 51.6 mg/g; quercetin content: 72.2 mg/g) extracted from Tartary buckwheat boiled noodles using 70% methanol as the solvent was found to have α-glucosidase inhibitory activity. As for fractions fractionated by silica gel column chromatography, the fractions rich in quercetin and rutin showed remarkable α-glucosidase inhibitory activity. Tartary buckwheat boiled noodles used as samples in this study contained quercetin produced from rutin by the action of rutinase, suggesting that both rutin and quercetin contained were involved in the α-glucosidase inhibitory activity of the dry solid extract. Changes in postprandial blood glucose levels were compared for boiled noodles made from two types of buckwheat (i.e., Tartary buckwheat and common buckwheat), revealing that blood glucose elevation after eating Tartary buckwheat boiled noodles was suppressed. The blood glucose level 40 minutes after eating Tartary buckwheat boiled noodles was significantly low (p<0.05). It can be concluded that this might be caused by the α-glucosidase inhibitory activity of rutin (270.0 mg) and quercetin (330.5 mg), which correspond to a total amount of 935 mg of rutin equivalents, in the gastrointestinal tract. As a result, the digestion of carbohydrates contained in the samples consumed and their absorption by the intestine might be inhibited, resulting in the suppression of increases in blood glucose levels. The presence of a certain amount of quercetin was considered to be key to the suppression of blood glucose elevation. It is important to control rapid postprandial blood glucose increases to prevent diabetes from developing or becoming serious. This study suggests the potential for Tartary buckwheat boiled noodles to contribute to diabetes prevention.