A network device 200 for relaying packets includes a network interface 220, a forwarding engine 240, a state change controller 274, a device state controller 276 and a device information table 278. The state change controller 274 and the device state controller 276 cooperatively determine whether a packet receiver port that has received a sleep notification packet among a plurality of ports included in the network interface 220 has setting of link aggregation. When link aggregation is set for the packet receiver port, the state change controller 274 and the device state controller 276 keep the packet receiver port in a power ON state, while all other ports, which belong to an identical link aggregation group are to a power OFF state.