A switch device includes a retaining unit, a switching processing unit, an identifying unit, and a rewriting unit. The retaining unit retains a flow table that maps each flow to a flag indicating whether the amount of transmitted data is equal to or more than a predetermined threshold. The switching processing unit stores a data packet received by a receiving buffer in one of a plurality of output queues provided for respective transmission ports based on the destination. The identifying unit identifies data packets included in a flow in which the amount of data is equal to or more than a predetermined threshold, from the data packets received by the receiving buffer. The rewriting unit refers to congestion notification information included in each of the identified data packets, and rewrites information indicating congestion to information indicating no congestion when the congestion notification information includes the information indicating congestion.