The present invention provides a thickening composition simultaneously exhibiting suitable thickening performance and superior usability, which contains N-long-chain acyl acidic amino acid and/or a salt thereof, an amphipathic substance, an inorganic salt, and water as essential components, and has a viscosity of not less than 200 mPa·s. By the addition of the thickening composition, moreover, cleansing compositions and cosmetic compositions for skin, hair and the like, which maintain thickening performance and usability, while containing N-long-chain acyl acidic amino acid and/or a salt thereof are provided.