PURPOSE: To prepare the titled compound useful as a perventive for radiation diseases or its intermediate, in high yield, without producing by-products, by reacting (2-aminoethyl) hydrogen sulfate with sodium thiosulfate, and hydrolyzing the product with a strong acid or hydrogen peroxide.

CONSTITUTION: 1mol of (2-aminoethyl) hydrogen sulfate which is a novel raw material having excellent economic value, reactivity, and safety, is made to react with 1W5mol of sodium thiosulfate at 4W7pH and about 100°Cfor several hours. The reaction product is hydrolyzed with an aqueous solution of a strong acid such as hydrochloric acid, sulfuric acid, phosphoric acid, etc. or hydrogen peroxide solution in nitrogen gas stream to obtain the objective compound while suppressing the production of di(2-aminoethyl)sulfide.