A packet routing apparatus has a routing information table comprised of a plurality of sub-tables. Each sub-table includes an entry of a first format indicative of routing information, and at least one of the sub-tables includes, in addition to the entry of the first format, an entry of a second format for designating another sub-table to be referred to. A routing processor of the packet routing apparatus refers to a sub-table designated by an input line interface. As a result, when the entry of the second format is retrieved, the routing processor executes routing of an input packet and header conversion by referring to another sub-table designated by the entry.