A radio-frequency identification tag communication device including a BFA weight-value setting portion operable to control a directivity of a transmitter antenna, and an adaptive processing portion operable to implement an adaptive control of a weight to be given to a received signal received by each of a plurality of antenna elements, on the basis of a reply signal transmitted from a radio-frequency identification tag, so that the directivity of the transmitter antenna is changed to a direction in which the frequency identification tag in question is expected to exist, and the weight to be given to each received signal is subjected to the adaptive control, whereby the sensitivity of communication of the communication device with the radio-frequency identification tag is improved.