PURPOSE: To reduce unreacted oil and to increase moisture content, in stripping a specific neutralized mixture, by together using an additive such as polyhydric alcohol, sodium or potassium secondary phosphate and sodium or potassium tertiary phosphate.

CONSTITUTION: 8W22C aliphatic primary alcohol is sulfonated or sulfated and the resulting reaction product is neutralized. An additive selected from polyhydric alcohol, polyoxyalkylene ether, polyoxyalkylene phenyl ether and a mixture thereof is added to the formed neutralized substance in an amount of 0.1W10wt% times said substance and one or more kind of sodium or potassium secondary phosphate and sodium or potassium tertiary phosphate is added thereto in an amount of 0.015W50pts.wt. of 100pts. of said additive. Next, an unreacted oil component is stripped from the neutralized mixture and said mixture is concn. so that the moisture content thereof becomes 120pts.wt. of 100pts. of a surfactant.