An automated bid decision system allowing a bidder to make a bidding for plural commodity items over a plurality of markets is disclosed. A data memory stores a logical formula representing a relationship among a plurality of bid items, a value table of the bid items, price information of the bid items in at least one market, a total purchasing fund, and a bidding strategy. A profit computation section computes a profit obtainable when at least one bid item arbitrary selected from the bid items is purchased, based on the value and the price information. A strategy computation section determines a list of bid items for which a bid should be made and a gross profit obtainable therefrom. A combination candidate is selected from the bid items based on the relationship formula and a possible profit obtainable from the selected combination candidate is computed. The final list of bid items are determined so as to maximize the possible profit within the total purchasing fund.