Abstract: An article sales data processing apparatus comprises a wireless tag reading unit configured to read data in a wireless tag attached to an article, a processing unit configured to process sales data for the article sold as one transaction, on the basis of the data in the wireless tag read in the wireless tag reading unit, a judgment unit configured to judge whether to invalidate each of the wireless tags whose data has been read in the wireless tag reading unit, and an invalidation unit configured to invalidate the wireless tag judged to be invalidated by the judgment unit.