To allow a public terminal to economically store the usage data for a prescribed period in the public terminal.

The public terminal that is operated on a station power supply in the case of a speech on the basis of use of, e.g. a card for a speech service, is provided with a RAM 13 that stores usage data such as a card number used for the speech and a call unit and with a flush memory 14 whose data can electrically be over-written and that can store the data for a prescribed period. A CPU 11 sequentially stores the data in each area of the flush memory 14 every time the RAM 13 stores the data at a speech and sequentially reads the data of a specified amount that are stored from the flush memory 14 and transmits the read data to a management unit when the flush memory 14 stores the data of the specified amount.