To provide a method and system for supporting electronic commercial transaction which can find a shop selling goods, which is suited for user's request condition, by using communication network by an easy operation in a short time.

An electronic commercial transaction service site 1 collects commodity information at regular intervals from a plurality of shop sites 2 prepared on communication network L, stores them as database 1a and updates it. The user searches the shop sites 2, which can sell the commodities, in the database 1 according to the requested condition of the commodities containing requested number of the commodities through a communication terminal 3, and the result information on the search is distributed to the user's communication terminal 3.