[Problem] To provide a novel medicine that is capable of promoting cholesterol metabolism to thereby treat, ameliorate or prevent various symptoms associated with increase in blood cholesterol level. [Solution] The present inventors newly found that arctigenin has an effect of promoting the conversion of cholesterol into bile acid. The present invention provides a bile acid synthesis promoter, a composition for promoting bile acid synthesis and a food composition for promoting bile acid synthesis each comprising arctigenin and/or arctiin as active ingredient(s).