1. A financial transaction processing system comprising: an integrated circuit card for use in financial transaction processing, said integrated circuit card including first data storage means having storage area for storing data specifying a plurality of transaction accounts corresponding to a plurality of financial institutions; and a terminal for communicating with said integrated circuit card, said terminal including account designating means for designating a specific account which a customer wishes to use, out of said plurality of transaction accounts corresponding to the plurality of financial institutions; said integrated circuit card further including transaction data outputting means responsive to said account designating means for reading out data specifying the account designated by said account designating means from the data specifying transaction accounts corresponding to said plurality of financial institutions stored in said storage area and for transmitting the read data to said terminal.