PURPOSE: To prepare the titled compound useful as a proliferation promoting factor for bifidus bacteria, etc. in high purity, by reacting calcium pantothenate with 2-aminoethanethiol sulfate, and puritying the product with a weakly basic anion exchange resin and a strongly acidic cation exchange resin.

CONSTITUTION: Calcium pantothenate and 2-aminoethanetiol sulfate are dissolved in water, and dicyclohexylcarbodiimide is added to the solution in the presence of pyridine, etc. The components are made to react with each other under ice cooling, and the reaction is continued at room temperature. The reaction mixture is filtered, the filtrate is passed thrugh a column packed with a strongly acidic caion exchange resin to remove pyridine, etc., and the eluate is passed through a column packed with a weakly basic anion exchange resin and eluted with an aqueous solution of sodium hydroxide. The eluate is passed through a column packed with a strongly acidic cation exchange resin, and the objective compound is separated from the eluate.