An electronic commerce for semiconductor products comprises a network, a client terminal, a connection server, a virtual production line, and a real production line. The real production line actually manufactures semiconductor products. The virtual production line provides a computer with substantially the same functions as the real production line and computes an optimal lot progress. The connection server connects the virtual production line to the client terminal via the network. When a condition is entered from the client terminal, the connection server transfers this condition to the virtual production line. Simulation is performed realtime for determining whether a product flows in the virtual production line under the transferred condition. The connection server transfers a simulation result to the client terminal. Based on the simulation result, a electronic commerce is conducted.