A nonreciprocal circuit device has a structure that allows a direct current magnetic field having an even density to be applied to a necessary portion of a ferrite without impairing a reduction in profile so as to improve insertion loss. The nonreciprocal circuit device, for example, a two-port isolator, includes permanent magnets, a ferrite to which a direct current magnetic field is applied by the permanent magnets, and a first center electrode and a second center electrode that are disposed on the ferrite. The permanent magnets are disposed so as to oppose principal surfaces of the ferrite. Portions of each of the permanent magnets opposing relay electrodes on top and bottom surfaces are preferably thicker than other portions thereof.