The invention provides a tag communication device, a tag moving direction detecting system and a tag moving direction detecting method able to detect the moving direction of a moving body attaching a RFID tag thereto by simple processing, and able to easily detect the moving direction even when its moving speed is increased. A scan antenna scans a beam of a transmitted radio wave toward a belt conveyer for conveying baggage with a RFID tag. ID is read from the RFID tag, and reading NO. and a scan angle are related and recorded to a measuring data table, and plot data are generated. These plot data are plotted in an XY coordinate system, and a plot graph is generated. Further, a linear approximate straight line is calculated from this plot graph, and a moving direction of the baggage is detected from an inclination value of the linear approximate straight line.