PURPOSE: To prepare the titled compound useful as a synthetic raw material of organic chemicals such as pharmaceuticals, agricultural chemicals, etc., from inexpensive low-toxic raw materials, in high yield, by reacting acrylonitrile with a thiosulfuric acid salt in a specific reaction system, and hydrolyzing the product in the presence of an acid.

CONSTITUTION: Acrylonitrile is made to react with a thiosulfuric acid salt (e.g. sodium thiosulfate, calcium thiosulfate, etc.) in a solvent such as water, alcohol, dioxane, etc. controlling the pH of the reaction system to 5W9, preferably 6W8, at a temperature between 40°C and the boiling point of the solvent for 30minW 5hr to obtan Bunte salt. The salt is hydrolyzed at a temperature between 60°C and the boilig point of the solvent for 30minW8hr in the presence of an acid such as sulfuric acid, hydrochloric acid, etc. to obtain the objective product. The acrylonitrile used as a main raw material can be prepared by the ammoxidation reaction of propylene. The amount of acrylonitrile is nearly equimolar to the thiosulfate, and tht of the acid is 0.5W5mol per 1mol of acrylonitrile.