Herein is disclosed a cosmetic composition comprising, as active ingredients, one or more members selected from the group consisting of mono-N-acylarginines and cosmetic powders whose surfaces have been treated with a mono-N-acylarginine (Ingredient A) and one or more members selected from the group consisting of water-soluble polymers and alcohol-soluble polymers (Ingredient B), which cosmetic composition is excellent in conditioning effects such as moist feeling and voluminous feeling in the case of hair cosmetics and excellent in feelings upon use such as smoothening property and moist feeling without sticky feeling and occlusive feeling in the case of skin cosmetics.