The importance of service industries is growing as the portion of the service sector increases fast in the recent decades. This research deals with service prototyping and testing in a service laboratory. While products are generally tested through prototyping in new product development processes, services are difficult to test because of the characteristic of service, intangibility. A service laboratory, named s-Scape, is the experiment environment which has been developed to test services in virtual space for the purpose of analysis and improvement of real-world services such as hospitals and automobile show rooms. In this research, we present a service prototyping tool and language to support service test in the service laboratory. We first analyze key elements of service prototypes, and then design the service prototype diagram (SPD) and the service prototype description language (SPDL). SPD, which is a variant of the service blueprint, is a graphical tool to be used to generate SPDL. SPDL is an executable language of describing a service prototype of a real-world service in extensible markup language (XML) to experiment the service environment in virtual space. SPD reflects the control and interface of virtual reality devices, as well as key elements of service modeling. SPD represents a service process in which service providers and customers interact with each other in a service scape.