To optimize an operation index for deciding a production schedule at the time of plurally batch-producing a plurality of brands.

At the time of planning the production schedule for producing the plurality of brands in a process having a batch process and a continuity process and a recycle process wherein there is an inter-series shared facility in a plurality of series, the production order of brands and the number of production batches decided in a production plan and a condition being restriction and a target operation index are formulized as a combinatorial optimization problem, and a production schedule fulfilling the operation index the most is selected from executable solutions acquired by calculation.