A semiconductor switch includes a main line, branch lines branching from the main line at the same branch point, switching devices shunt-connected between one of the branch lines and ground and operated so that the one of the branch lines is connected to and disconnected from ground, a main terminal connected to an end of the main line, and branch terminals connected to an end of one of the branch lines. The impedance of one of the branch lines, as seen from the branch point, is conjugately matched to the combined impedance of the main line and the rest of the branch lines, as seen from the branch point, the one of the branch lines transmitting an RF signal, and the rest of the branch lines blocking the RF signal.