PURPOSE: To apply the optimization control method to a large-scale press and to facilitate optimum control over the process by performing optimum calculation without correcting measurement data, and eliminating an error due to linearization and then shortening the time for output value determination.

CONSTITUTION: The plant consists normally of a nonlinear model, and a nonlinear model calculation part 2 holds a detailed model as a nonlinear model which is previously generated as a plant model and also inputs specific data to calculate an output value. A linear model generation part 3 expands the detailed model nearby an operation value to find an approximate model (linear model). At this time, the output (various measurement data) of the plant 1 is referred to. A restriction range generation part 5 generates a restriction range applied by a linear optimization calculation part 6 according to restriction values set by a restriction setting part 4 and the operation state of the process. The linear optimization calculation part 6 makes the linear model. obtained by the generation part 3, relative to perform the optimum calculation.