In this paper, a model of cost evaluatino for computer software development is proposed . This model is designed to cope with various development environment since the development cost is directly dependent on the development environments. The model that satisfies the users request is turned out to be a function point model. For the future research , a model that contain new technique and new development environment and an imaginative model are desired . Also, in order to effective cost estimation a systematic research on structure of software development , establishment of standard development methodology, project management and technique are desired.