“Group Scheduling,” which is operations scheduling based on the Group Technology concept, was analyzed in a multistage manufacturing system. In the case of fabricating multiple parts (jobs) grouped into several group cells, both optimal group and optimal job sequences were determined such that the total flow time (makespan) was minimized, by means of the branch-and-bound method. In addition, optimal machining speeds to be utilized on multiple stages (machines) for each job were determined to reduce the total production cost as much as possible. Optimizing algorithms for this Group Scheduling Technique were also presented with numerical examples.