Recently, economic conditions have been worsening and the structure of industry has been changing dramatically. A highly creative service has become important topic since its creative contents are one of the effectiveness ways to differentiate a firm's services from those of its competitors. To cope with this condition, service engineering is proposed. In service engineering, we have already proposed the support method for service design with the aim of acquiring creative solutions based on the similarity among existing service cases. It is important for a service design to acquire multiple domain knowledge efficiently. In this paper, we propose a support method with the aim of acquiring "If-Then format" sentences which are multiple and useful for a service design by using the resource on the web. Finally, the method is verified through the case study of a service.