Abstract: An article sales data processing apparatus has an electronic tag data memory, and an article item buffer. A CPU judges whether the same data as the electronic tag data read by the electronic tag reader is stored in the electronic tag data memory. If the same data is already stored, the CPU discards the electronic tag data read from an electronic tag. If the same data is not stored, the CPU adds the electronic tag data read from an electronic tag to the electronic tag data memory. Based on this electronic tag data, the CPU obtains article sales data, and adds the data to the article item buffer. When registration/closing of one transaction is declared, the CPU executes closing of one transaction based on the article sales data in the article item buffer. After the closing is completed, the CPU clears the article item buffer.