A switch device includes a relay unit relaying communication data when information processing units included in an information processing apparatus perform communications with external devices; an address learning unit registering ports receiving the communication data in association with addresses indicating transmission sources of the communication data; and a band control unit controlling a bandwidth to be allocated to the communications by setting a first port and a second port of the ports to belong to a same group and by setting the first port and the second port to belong to different groups based on a number of addresses registered by the address learning unit in association with each of the ports.