There are three viewpoints involved in software project management: process management, quality management and cost management. Software projects must be managed on the basis of these three viewpoints. However, in many cases process management, quality management and cost management systems are built separately as individual systems respectively. Construction of software project management systems which these three functions are integrated has been rare. Therefore, in order to construct a system integrating these functions, the authors clarify the significance of integration of application systems. And then the authors unveil the structure of a software project management system that process management system, quality management system and cost management system are integrated by using an object oriented database.