It is intended to provide an emulsifier having a high emulsifying capability and containing highly water-soluble polysaccharides as the active ingredient, a process for producing the same and an emulsified composition using the emulsifier. Namely, an emulsifier which is obtained by extracting soybean or a processed soybean product within an acidic region of pH 2.4 to 4.0 under heating to a temperature of 100.degree. C. or higher. This emulsifier, which contains polysaccharides, shows a remarkably elevated emulsifying capability compared with the existing water-soluble soybean polysaccharides. A process for producing the same and a stable emulsified composition in which this emulsifier is used.