An offsetting comparator device includes master and slave comparator circuits and a reference differential voltage generator. The master comparator circuit supplies a sensed current corresponding to a potential difference represented by a differential signal on a transmission line. The reference differential voltage generator generates a reference differential voltage based on an intermediate potential of the differential signal. And the slave comparator circuit supplies a current corresponding to the potential difference as offset current. The offsetting comparator device outputs a differential current between the sensed and offset currents and therefore shows an offset in its input/output characteristics. The master and slave comparator circuits have the same circuit configuration. Thus, if the characteristic of the sensed current output from the master comparator circuit has changed due to a potential level variation of the differential signal, then the characteristic of the offset current also changes similarly. Thus, the offsetting comparator device can obtain a constant offset voltage even if the potential level of the differential signal has changed.