Disclosed herein are branching filter suitable for connection with a transmission/reception integrated radio device, and a multiplex transceiver which utilizes the branching filter. A band pass filter unit separates an outgoing wave from an incoming wave. An antenna duplexer transmits an outgoing wave from the band pass filter unit to an antenna, and transmits an incoming wave from the antenna to the band pass filter unit. The band pass filter unit has two ports on the antenna side, and one port on the radio device side. A transmission/reception integrated radio device is connected to the port of the branching filter on the radio device side.