PROBLEM TO BE SOLVED: To provide a novel oligosaccharide which uses mannose and fructose as constituent sugars, a method for producing the oligosaccharide, an improving agent for intestinal bacterial flora using the oligosaccharide as an active ingredient, a culture medium for microbial cultivation containing the oligosaccharide, and an anticancer agent using the oligosaccharide as an active ingredient.SOLUTION: The invention provides mannopolyocyl fructose represented by the following formula (1) (where, n represents an integer of 0-8) and an improving agent for intestinal bacterial flora containing the mannopolyocyl fructose represented by the formula (1) as an active ingredient.
