The purpose of the present invention is to provide a nonreciprocal circuit element such that low input impedance is achieved and an increase in the number of components in a transmitting side circuit and the cost thereof are minimized to the extent possible. A nonreciprocal circuit element (isolator) is provided with a ferrite (32), a first and a second center electrode (35,36) (a first and a second inductor (L1, L2)) arranged on the ferrite (32) so as to be mutually insulated from and intersecting with each other, and a permanent magnet for applying a DC magnetic field to the intersection portion of the first and the second center electrodes (35,36). One end of the first center electrode (35) is defined as an input port (P1) and the other end is defined as an output port (P2). One end of the second center electrode (36) is defined as an input port (P1) and the other end is defined as a ground port (P3). A resistor element (R) and a capacitor element (C1) connected mutually in parallel are connected in series between the input port (P1) and the output port (P2). By relatively increasing the inductance of the second center electrode (36), the input impedance can be decreased.