PURPOSE: To provide an economic and efficient method for controlling optimum cutting lengths of rolling materials even for a plurality of orders for different lengths of products and different numbers of components.

CONSTITUTION: In No.1 coordination line, rolling expansion lengths of materials in materials storage 12 are calculated by material expansion length calculator 13 and are stored in memory 16. Materials in heating furnace 1 are rolled by rolling machine 2 and then are temporarily placed in No.1 materials depository 3. Next, materials are cut and aligned by cutter 4, which is controlled by control device 14. Then, they are collected in lot collection place 7. In No.2 coordination line, secondary materials sent to No.2 materials depository 8 are cut into product lengths by cutter 9. In this case, a function that expresses the performances of the processes of both coordination lines is obtained in advance, and cutting lengths at No.1 coordination line are determined such that the function is made a minimum.