To easily obtain a production stage which has high productivity.

At an assembly stage for electronic equipment assembly as an example of a production stage for producing a product, a process is formed by grouping operations which should successively be performed. The assembly stage is implemented by a combination of processes and the combination having the smallest number of processes is selected while the operation with restrictions of an operation time. By this combination, the process productivity obtained by dividing the production the output by the number of processes and the operation time can be maximized.