Under the open innovation paradigm, identification of application areas of the internally developed technologies is important to maximize the profits from them. However, many companies have failed to identify opportunity for additional applications. The fundamental reason is that companies have insufficient understanding of the potential applications of their technologies, because different industries use far different technologies and technological terminologies. However, technologies can be linked with outside industries by analyzing them from the functional perspective, because functions used in different industries are generally similar. Therefore, this article proposes a function-based patent analysis to identify the potential application areas of a technology. In general, technologies in a patent are invented for use in a specific industry, and thus a patent can be categorized into a specific industry. By identifying patents which contain a specific function, industries that use the function can be identified. Industries in which the importance of the function is relatively high can be considered as areas in which technologies performing the function have potential to be applied, and the proposed indexes evaluate the relative importance of the function withieach industry. Finally, the practical usefulness of the proposed method wa verified by identifying the potential areas in which vortex reduction technology can be applied