Since CAD data is used as master data throughout the lifecycle of a product, it is important to provide a means for efficiently sharing CAD data among systems used for collaborative product development. Web Services, a type of distributed object technology, is adequate for this purpose; in a previous study [7], the authors proposed the architecture of Web Services for CAD (WSC) for the retrieval of CAD data. CAD data are classified into CAD assembly and part data. Since product design is typically modeled in the form of CAD assembly data, it is worth to consider this application when implementing a service for CAD data retrieval. In this study, the authors first propose a concept of parallel Web Service, which is an extension of WSC and whose goal is the rapid retrieval of CAD assembly data. They then discuss the technical details that can lead to its realization. Finally, experimental results regarding the performance of assembly data retrieval by the parallel Web Service are presented and compared with analogous performance by a single Web Service.