With the improvement of the Information Technology and the change of the business environment, the dependency of business on the Information Technology shows sharply increase. The Information Technology, however, is centered on the support of the technology viewpoint and thus the influence and effect of Information Technology on the business is hardly analyzed. The information system, therefore, requires not only technology-centric support management but service-oriented and systematic introduction of Information Technology Service Management(ITSM). The domestic ITSM market is currently expanding into variety of industries like finance, telecommunication, manufacturing and public service and at the same time the consequent reconstruction process of information system is continuously under way so as to qualify for the ISO 20000 certification. Especially the public organizations rapidly adopt the ITSM, in order to improve the quality of public service together with a goal of realizing the electronic government and of managerial innovation. The existing ITSM still, however, shows the tendency of depending only on the system construction and the management on the visible requirements whereas the overall process is not likely being improved. Hence, this study suggests, focusing on the life cycle of service, the model of ITSM based on Information Technology Infrastructure Library(ITIL) v3 which is appropriate for the public service. We expect, as stated in this study, that our ITSM model shall be widely accepted to the public agencies who promote the advance campaign by setting up the ITSM or reconstructing the existing process.