1. A firewall policy inspection apparatus comprising: an intrusion prevention rule obtainment unit for obtaining intrusion prevention rules from a target firewall policy; an anomaly rule detection unit for detecting an anomaly rule in a relationship between the intrusion prevention rules; and a screen display unit for displaying an anomaly rule graph on a screen using results of the detection, wherein the intrusion prevention rule obtainment unit obtains a protocol, a source Internet Protocol (IP) address, a source port, a destination IP address, a destination port, a policy action, and a rule sequence that are components of the intrusion prevention rules, wherein the screen display unit is configured to, if the anomaly rule is detected in a relationship between a first intrusion prevention rule and a second intrusion prevention rule, display an anomaly rule graph in which a number of the first intrusion prevention rule, the detected anomaly rule, and a number of the second intrusion prevention rule are sequentially connected, wherein the screen display unit further displays an intrusion prevention rule graph in which the source IP address, the destination port, and the destination IP address are sequentially connected, and wherein the screen display unit is configured to, if a user input for selecting a graph node corresponding to any one of the number of the first intrusion prevention rule, the number of die second intrusion prevention rule, the anomaly rule, the source IP address, the destination IP address, and the destination port is received, update the screen in correspondence with the selected graph node.