PURPOSE: To eliminate the need to insert and extract cards frequently by putting plural cards in a card storage part and then drawing a top card when the call rate becomes 0.

CONSTITUTION: The cards 8 are put in the card storage part before a portable telephone set is used. When the portable telephone set is in use, a call rate reader writer 4 recognizes only the top card and performs rate processing. When the rate of the top card becomes small, an alarm 7 generates an alarm tone first. When the rate reaches 0, the alarm 7 sounds again. At this time, the top card is drawn out with a finger 9. Then a card which becomes a top card is used next. A card use state writer 5 adds a mark to the used card.