This invention provides a novel material having a vasodilator action thereby suppressing or ameliorating various human diseases and disorders. A composition comprising, as an active ingredient, peptides obtained by hydrolyzing proteins such as proteins derived from a seaweed selected from layer, wakame, edible brown algae, sea tangle, chlorella and spirulina, proteins derived from a plant selected from soybean and sesame, proteins derived from a fish selected from bonito, mackerel, saury and horse mackerel, proteins derived from milk proteins selected from powdered skim milk and whey, proteins derived from an animal selected from cattle and swine, and collagen like proteins derived from bovine collagen, porcine skin collagen and fish scale-derived collagen is used as a pharmaceutical composition and a health food composition thereby exhibiting a vasodilator effect by which various phenomena caused by a reduction in blood stream, such as stiff neck, headache and poor circulation, can be suppressed or ameliorated.