The present invention provides a postprandial hyperglycemia-improving agent, which is useful as a food or a pharmaceutical product. The postprandial hyperglycemia-improving agent includes, as an active ingredient, a fat and oil composition containing 5% by mass or more of a diglyceride and/or a monoglyceride in which an ω9 unsaturated fatty acid content in constituent fatty acids is 35% by mass or more.