A reader/writer apparatus includes a roller to transport a sheet along a transport path. The sheet can labels disposed thereon spaced from each other. Each label includes a wireless tag, such as an RFID tag. A wireless tag reader has an antenna disposed on the transport path and reads identification data from wireless tags when the sheet is being transported. A processor operates to store the identification data read by wireless tag reader in association with a signal intensity of a response signal from the wireless tag and a position of the sheet on the transport path at the time of the reading of the wireless tag. A position of the sheet on the transport path for each wireless tag can be specified for writing data into the wireless tags based on peak signal intensity associated with identification data.