A packet relay apparatus keeps only packets specified as authentication target packets of MAC address authentication, to reduce the number of packets to be transferred from H/W to a CPU. In addition to a source MAC address, the authentication target packet of MAC address authentication is specified by an Ethernet type, a destination IP address, a protocol, a source port number and a destination port number of TCP/UDP, and the like. In this way, the packet relay apparatus excludes a terminal not transmitting authentication target packets of MAC address authentication, from the MAC address authentication target, while allowing selection from other authentication methods such as Web authentication and IEEE802.1X authentication.