A packet relay device including a plurality of queues which store packets waiting to be transmitted, a congestion detection unit which detects a congestion state of the plurality of queues and selects one or more queues from among the plurality of queues based on the congestion state, a distribution unit which separates a packet addressed to one or more of the queues selected by the congestion detection unit from a sequence of packets before being stored in the plurality of queues, and a discard unit which discards, at a prescribed probability, a packet addressed to one or more of the queues separated by the distribution unit.