Service industry accounts for lager fraction of GDP. Because the service productivity is not high, it is important to enhance service productivity. In this paper, in order to improve service productivity, the cases using scientific and engineering approaches were introduced. The cases used the simulation model with POS data in retail store. First case, the simulation model of customer behavior was constructed and utilized to examine customer flows, particularly the customer waiting time at the casher register in retail store. Second case, the simulation model of staff operations was constructed to determine the optimal number of clerks taking into account operation type, operation frequency, and staff scheduling. These cases were applied the "the optimal design loop" using simulation. As a result, store management problems and the staffing problems can be solved easily and effectively.