An isolator includes first, second, and third center electrodes coupled in a high frequency manner with a ferrite member to which a direct-current magnetic field is applied by a permanent magnet. The first and third electrodes do not intersect with each other, and intersect with the second electrode in a mutually insulated state. Connection is established so that a magnetic field generated when a current flows from one end to the other end of the first electrode, and a magnetic field generated when a current flows from one end to the other end of the third electrode have the same phase and direction. A capacitor and a resistor are connected in parallel to the electrode, a capacitor is connected in parallel to the electrode, and a capacitor and a resistor are connected in parallel to the electrode. One end of the first electrode and the other end of the third electrode define balanced input ports, and the other end of the first electrode, one end of the second electrode, the other end of the second electrode, and one end of the third electrode define balanced output ports.