A compact, inexpensive nonreciprocal circuit device which provides a large attenuation in a particular frequency band, and a communication device incorporating the same. A series resonance circuit in which an inductor and a capacitor are connected in series to each other is connected between a first port of a central conductor and the ground, capacitors are connected between the ground and a second and a third ports of other central conductors and the ground, and a terminating resistor is connected to the third port.