Recently, the theory of open innovation emerges as a new innovation paradigm. This paper aims to examine open innovation activities of SMEs. Many firms tend to search new knowledge from various external sources and to pursue to achieve innovation resources or knowledge of external innovators. Particularly, this paper focus on the process of external knowledge networking and open innovation occurred in the process of technology innovation. The data used in this study were those that had been collected for total 3,400 sample SMEs that had conducted R&D. and in-depth interviews were conducted with 14 SMEs located at Chungbuk-Technopark. Empirical findings can be summarized as follows; SMEs tend to search new knowledge from various external sources and to pursue to achieve innovation resources or knowledge of external innovators, because they have lack of innovation resources. therefore, the conducting of open innovation affected positively the innovation performance of SMEs. In addition, empirical findings also indicated that expanding flexibility of labor market enhances open innovation activities of SMEs.