IP addresses included in a route table are segmented so as to be able to be retrieved all together, and are retrieved at a high rate. As means for retrieving the IP address, a pointer table 200, a secondary pointer table, a local table, and a route table are provided, and a table with a numerical value comparing function is also provided when the further segmentation is necessary. In the retrieval for the ACL table, a fixed length data table of fixed length data configured in the ACL table is generated, and the ACL table is retrieved by using a retrieving method for retrieving the route table. Such tables are provided with a table manager 600 as means for efficiently composing and managing the table, and managing to prevent the retrieving operation from being obstructed.