Abstract: The present invention relates to a credit card transaction authentication system and method using a mobile terminal. There is provided a credit card transaction authentication system using a mobile terminal for performing a work of credit card authentication for a relay system of a VAN company connected between an approval system of a credit card company, which can approve a credit card settlement of the prices, and a transaction approval terminal, which requests credit card transaction approval by means of contactless radio-frequency identification for the mobile terminal containing a transponder therein. The present invention provides advantages that a cumbersome procedure in which the credit card should be handed over and taken again by the user upon making the credit card settlement can be eliminated, and stability of credit card information can be enhanced so that a commercial transaction can be briskly made.