To make products have more added values largely from knowledge and services, we need new engineering discipline to look at services, called 'Service Engineering.' Services allow service providers to enable their flexible individualization and enhancement according to individual customer requirements. To do so, service providers need to consider customer requirement through whole life-cycle of a service, and to provide relationship-based services rather than transaction-based services. This paper, first dines life-cycle of a service, and then proposes a customer scenario model to extract customer requirements in consideration of whole life-cycle of the service.