A method of heightening the emulsifying power of gum arabic without causing coloration or offensive-odor emission. The method comprises: a step in which an aqueous solution of gum arabic which has undergone no heat treatment is prepared in a concentration of 50 mass% or lower; and a treatment in which the aqueous solution is held under the conditions of a temperature lower than 60°C for at least 6 hours. Thus, a modified gum arabic can be obtained which is colorless, emits no offensive odor, and has excellent emulsifying power. The modified gum arabic is suitable for use as an emulsifying agent for beverages, snacks, chewing gums, oily perfumes, oily dyes, oil-soluble vitamins, etc.