To explore the technology opportunity is essential for a company and an industry so that the company can consider the allocation of R&D investments and the industry can observe the developing directions of rare topics. Patent data contains plentiful technological information from which it is worthwhile to extract further knowledge. Therefore, a research framework for exploring the technology opportunity has been formed where clustering method is employed to generate the clusters, similarity measurement is adopted to identify the variant patents, and association analysis is used to recognize the focused rare topics. Consequently, the clusters were generated and named, the variant patents were found, the focused rare topics were recognized, and the technology opportunities for companies were discussed. Finally, the variant patents and the technology opportunities would be provided to assist the decision makers of companies and industries.