To provide a packet transfer device that can prevent a phenomenon of reversal of a sequence of packets in a plurality of paths and almost fully use bands of ports set at a LAG without deviation of a traffic to a particular port.

The packet transfer device includes: a means (an encapsulation section 112 and a sequence number applying section 113) for encapsulating all the pieces of information including the traffic for a LAG port into a capsule with a sequence number; and a means (packet reception section 101) for uniformly transmitting/receiving the capsule with the sequence number to/from the LAG group port.