In Service Engineering, a service is represented with its functions and the entities that are needed to express the functions. And in each entity, its attributes that are thought as important variables for the function appearance are described. In this paper, the authors regard a concrete improvement of service delivery process as the purpose of our study, and classify the way of service improvement. On the other hand, at a conceptual design phase, to evaluate the entities' attribute value is effective for the improvement of service, however it is not clear which entity is fit to express a certain function in the first place. Therefore, this paper proposes the analytical method to discriminate the fitness of entities for the improvement of service delivery process.