A relay device includes a first connecting unit, a second connecting unit, a first notifying unit, a second notifying unit, and a communicating unit. The first connecting unit is connected with a first interface of a first device, the first interface being not compliant with USB (Universal Serial Bus) standard. The second connecting unit is connected with a second interface of a second device, the second interface being compliant with the USB standard. The first notifying unit notifies the second device that the relay device is a USB device. The second notifying unit notifies the first device that the second device has been connected to the second connecting unit. The communicating unit relays communication carried out between the second device and the first device.