1. A relay apparatus comprising: an associative memory for storing a first address group having a plurality of associative memory addresses and specifying a first associative memory address corresponding to designated data in the first address group; a conversion unit for converting the specified first associative memory address to a contents memory address; and a contents memory for storing a plurality of contents memory addresses and a second address group having a plurality of associative memory addresses that are same as the plurality of associative memory addresses in the first address group and respectively correspond to the plurality of contents memory addresses, and outputting a second associative memory address corresponding to the converted contents memory address out of the second address group.