To provide an opening method for a temporary account and its system capable of eliminating an uneasy feeling and a resisting feeling against unfair use and opening at a simple procedure so that a customer notifies others of an account used every day.

When opening a temporary account, the customer operates a selection button instructing a transaction selection screen of an ATM system 10 to open the temporary account. Based on an input signal, a host computer 30 of an integrated center 3 of a bank or the like performs a series of procedural control including issue of a card for a temporary account as a cash card from the ATM system 10. Card information of a cash card for a parent account of the customer inserted into the ATM system 10 is read out, and a parent account identification module 31 and a temporary account opening module 32 of the host computer 30 performs necessary information processing after identifying the customer as a proper client by means of input of a personal identification number, and the card for a temporary account as a cash card is issued and delivered to the customer from the ATM system 10. A temporary account closing module 33 monitors during a period of the temporary account specified by the customer, and carries out invalidating process by closing an expired temporary account.