There is disclosed a detergent composition containing, as an essential ingredient, at least one member selected from three types of .alpha.-sulfo-fatty acid derivatives as represented by following formulas (1), (2) and (3): ##STR1## where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are each an alkyl group or an alkenyl group, each having from 6 to 24 carbon atoms; R.sub.5 is an alkyl group having from 1 to 4 carbon atoms; M.sub.1, M.sub.2, M.sub.3 and M.sub.4 are each a hydrogen atom or a cation capable of forming a salt; AO is an oxyalkylene group or a polyvalent alcohol residue; and p, m and n are each a positive number. The detergent compositions are very low in irritability to the body and have a low critical micelle concentration and a low Krafft point. Further, they are highly soluble in water and they can be used in the form of powder or liquid.