There is provided a vasodilator having an endothelium-dependent vasodilator effect, a prophylactic of arteriosclerosis, and functional food having an endothelium-dependent vasodilator effect, which is suitable for daily and regular intake and excellent in safety. The vasodilator and the functional food according to the present invention are characterized in at least one of the tripeptides Val-Pro-Pro and Ile-Pro-Pro, or a proteolytic product containing Val-Pro-Pro and/or Ile-Pro-Pro, contained as an active component.