To enable an electronic commercial transaction utilizing a communication terminal of move object adaptable to various communication systems or browsers.

A client 20 accesses a selling site 11 by means of a portable telephone 21, reads information such as price or date of delivery of an article, selects the article desired to purchase on the basis of the provided information and transmits order data to the selling site 11. When the order data are received, the selling site 11 transmits information on the article determined to purchase by the client onto the liquid crystal display screen of the portable telephone 21 as image data based on a bar code. The client 20 visits a convenience store and reads this bar code by means of a bar code reader 32 connected to a POS terminal 31. By determining a method for settlement and article receiving in this case, the transaction is established.