A high-frequency signal branching device comprises a main body having an input terminal and an output terminal for connecting trunk cables on an input and an output side, respectively, and a branch body having a branch terminal for connecting a branch cable. This construction allows the number of branch terminals to be increased by replacing the branch body while keeping the main body intact. A branching circuit for branching a high-frequency signal from the trunk cable is provided in the branch body. Accordingly, the branching circuit also can be replaced by replacing the branch body.