An article sales data processing apparatus has an electronic tag data memory and an article item buffer. In the case where the same data as electronic tag data read by an electronic tag reader is not stored in the electronic tag data memory, the read electronic tag data is added to the electronic tag data memory. When the operating mode is switched to the cancel mode, data in the electronic tag data memory is cleared. In the case where the input mode is selected, article sales data is acquired based on the electronic tag data added to the electronic tag data memory and the acquired article sales data is added to an article item buffer. In the case where the cancel mode is selected, the article sales data acquired based on the electronic tag data added to the electronic tag data memory is deleted from the article item buffer.