This invention provides a pharmaceutical and functional food which are made of a safe food ingredient or nutrient which has been used for a long period of time, and which have tranquilizing effect such as anti-anxiety effect, anti-depression effect, and anti-stress effect. The tranquilizer of the invention contains vitamin K as an active ingredient. Vitamin K is preferably menaquinone-4 and/or menaquinone-7. This invention also provides a supplement, health food or functional food for tranquilizing purpose that contains vitamin K as an active ingredient.