To provide a method and a system which can smoothly make payment using a mobile-phone without using an expensive mobile type CAT terminal.

Prescribed data (ID, contract number, amount, etc.) are input by a first mobile phone (salespeople's mobile phone), and the data concerned is transmitted to a bar code conversion server and converted into the bar code for payment (100-102). The bar code concerned is sent to the first mobile phone and the bar code is displayed on the screens (103, 104). The bar code concerned is shot and read by a second mobile phone (visitor's mobile phone) (105). Read bar code is decrypted (106), decrypted data of bar code is transmitted to an AP server (107, 108), information for performing payment by the AP server is generated (109) and the information is transmitted to a payment server from the AP server (110). If payment processing is performed by the payment server, the result is returned to the AP server and the mobile phone (111-116).