A reader/writer (RW) requires identification information pieces of respective plural IC cards (A, B, C). The plural IC cards return the respective identification information pieces in response to the requirement by the reader/writer. Logical addresses are assigned to some IC cards among the plural IC cards respectively to cause the reader/writer to select them in response to the return of the identification information pieces by the plural IC cards. The IC cards selected by the reader/writer are controlled. The reader/writer cancels the assignment of the logical address to one of the selected IC cards. The logical address, the assignment of which has been canceled by the reader/writer, is assigned to an IC card among the plural IC cards to which any logical address has not been assigned yet. The IC card to which the logical address has just been assigned is controlled.