A filtering rule analysis system for analyzing the rules of a packet filtering process that is set in network devices includes: a rule storage for storing sets of rules for which an order of priority has been established; a matrix generator for generating matrix spatial data that contains information of the order of priority and that indicates the correspondence relation between a minimum region identified by starting points and end points of ranges of packet attributes described in each rule as the condition of application of that rule and those rules; and an overlap analyzer for referring to the matrix spatial data to analyze overlap between the rules.