A data management system is provided that manages sets in an orderly fashion.Sets are hierarchically organized according to implications thereof and stored in a set storage device 20. When a set in the relatively upper level of the hierarchy is specified among the hierarchically structured sets, a main controller section 10 performs a logical operation on all sets that belong to lower levels of the hierarchy thereof, and causes a display device DP to display a result of the logical operation as contents of said set specified.