Wireless transmission system, relay device, wireless sink device, and wireless source device

A wireless transmission system is provided that can minimize the control command transmission amount by operating a plurality of sink devices in conjunction with each other with respect to each group. The wireless transmission system includes: a bridge device (1) which wireless-transmits an AV content; and a plurality of wireless sink devices (5, 6) which reproduce the wireless-transmitted AV content. The bridge device (1) has a group identification table which stores a group identifier for identifying a group formed by the wireless sink device (5, 6). The bridge device (1) adds a group identifier extracted from the group identification table to a control command for controlling the sink devices (5, 6) and wireless-transmits the control command having the group identifier. The wireless sink devices (5, 6) receive a control command wireless-transmitted from the bridge device (1) if a corresponding group identifier is added to the control command.