PURPOSE: To obtain the subject agent for improving water retention of a water- in-oil emulsion of fat and oil composition having high water content such as low-fat margarine, extremely bettering stability of the composition during its production or preservation, comprising edible fine powder as an essential component.

CONSTITUTION: The objective agent for improving water retention comprises edible fine powder (e.g. a microfibrillated cellulose, microfibrillated chitin or microfibrillated chitosan) as an essential component. The fine powder, for example, is obtained by treating pulp, linter, chitin or chitosan by a high-pressure homogenizer. In the case of producing a water-in-oil emulsion of fat and oil composition having high water content by using this agent, the amount of the agent used is preferably 1-2wt.%.