Hydroxyalkanesulfonic acids represented by the general formula I, (wherein R represents a lower alkyl group containing 1 to 10 carbon atoms) and their derivatives such as alkali metal salts thereof are novel compounds prepared by, for example, reacting alpha-alkylstyrene with hydrogensulfite ion in an aqueous medium in the presence of oxygen. They are useful as starting materials for producing amidoalkanesulfonic acid derivatives for use as dispersing agents for lime soap, water-soluble high-molecular materials, and fiber-modifying materials.