We present template-guided concolic testing, a new technique for effectively reducing the search space in concolic testing. Addressing the path-explosion problem has been a significant challenge in concolic testing. Diverse search heuristics have been proposed to mitigate this problem but using search heuristics alone is not sufficient to substantially improve code coverage for real-world programs. The goal of this paper is to complement existing techniques and achieve higher coverage by exploiting templates in concolic testing. In our approach, a template is a partially symbolized input vector whose job is to reduce the search space. However, choosing a right set of templates is nontrivial and significantly affects the final performance of our approach. We present an algorithm that automatically learns useful templates online, based on data collected from previous runs of concolic testing. The experimental results with open-source programs show that our technique achieves greater branch coverage and finds bugs more effectively than conventional concolic testing.