Switching characteristics in an SPDT switch are improved to reduce the rise delay in a low power slot following after a high power slot. Control terminals of an SPDT switch are respectively provided with backflow prevention circuits. The backflow prevention circuit is configured to have two transistors and a diode. In a transmission mode, for example, when a time slot where a high power passes through transistors is followed by a time slot where a low power passes through, the electric charges accumulated in the gates of the transistors are blocked. In the case where the transistors are in the OFF state, the electric charges accumulated in the gates of the transistors are immediately discharged to allow the transistors to be completely turned OFF.