Provided is a substance which is a safer and more commonly-consumed food ingredient that increase the testosterone level. The testosterone enhancer of the invention comprises vitamin K as an active ingredient. The vitamin is preferably menaquinone-4 and/or menaquinone-7. This enhancer is useful as pharmaceutical agents, supplements, health foods or functional foods for the prevention, amelioration and/or treatment of a condition or disease induced by the decreased testosterone level.
