This flux for submerged arc welding is characterized by containing from 1% by mass to 25% by mass of an oxide of an alkaline earth metal, and is also characterized in that the oxide of an alkaline earth metal is contained in a liquid glass structure. It is preferable that the alkaline earth metal is one or both of Ca and Ba. It is also preferable that the water content of this flux as determined in accordance with JIS K 0068 (2001) is 200 ppm or less immediately after drying and is 1,000 ppm or less after 24-hour moisture absorption.