Method for producing a β- mercapto carboxylic acid

Method for producing a β- mercapto carboxylic acids of the present invention has the Step wherein step neutralized the reaction solution obtained in the acid in a, to obtain a reaction liquid containing a compound represented by the following general formula (4) represented by β- mercapto carboxylic acids and the following general formula (5) and b, The reaction liquid obtained in step b was purified by distillation, and step c to obtain a β- mercapto carboxylic acid represented by the general formula (4), The distillation residue containing the compound represented by the general formula (5) in step c, and a step d back to the step a, a.