A packet processing device includes a first search table in which an entry including an index value and a destination address is registered and a second search table in which a combination of header information and a destination address is registered. The packet processing device receives as an input a combination of header information and a destination to be registered and calculates an index value by one-way function calculation using the input header information. If the calculated index value is different from the existing entry in the first search table, the calculated index value and the input destination are registered as a new entry in the first search table. If the calculated index value is the same as the index value of the existing entry, a combination of the header information and the destination address represented by the existing entry is registered together with a combination of the inputted header information and the destination address in the second search table, and the destination address of the existing entry is deleted. By using the header information of a transfer packet, the packet processing device searches the first and the second search tables in parallel for the destination of the packet.