To easily obtain the subject compound in high yield by reaction of alkylene oxide(s) with a sulfamic acrid metal salt in the presence of an alkaline catalyst.

This compound is obtained by reaction of (C) an alkylene oxide (pref. at least one kind selected from ethylene oxide, propylene oxide, 1,2- butylene oxide, 2,4-butylene oxide and 1,4-butylene oxide) with (B) a sulfamic acid metal salt (pref. sodium sulfamate or potassium sulfamate) in the presence of (A) an alkaline catalyst (pref. an alkali metal hydroxide). It is preferable that the component B be dispersed in an inert organic solvent to be in a slurry with which the component C is made to react.