Process planning is essential for achieving a sophisticated manufacturing system, and computer-aided process planning (CAPP) have been discussed. Considering recent requirements for realizing agile manufacturing, a set of flexible CAPP methods have been developed, in which process planning for one product using one machine is dealt with. In actual manufacturing, multiple workpieces are usually machined with multiple machine tools in the same period, and pursuing optimality for each product independently may result in poor productivity. For this reason, integration of process planning and production scheduling was performed by formulating the integrated problem as a 0–1 integer programming problem. However, this formulation involves huge computational load. This paper provides an improved method where the integrated problem is formulated as a mixed integer programming problem.