Substance derived from grifola frondosa for inhibiting increase of postprandial hyperglycemia

Provided are a pharmaceutical product, food or drink, or other product wherein it is possible to safely treat or improve postprandial hyperglycemia without causing any side effects. A substance containing a moiety of glycoproteins, which has the extract, extracted fraction, and water extract of Grifola frondosa as the main component, was discovered to be effective in safely inhibiting the increase of postprandial hyperglycemia without causing any side effects.