Lock is a frequently-used synchronization mechanism to enforce exclusive access to a shared resource. However, lock-based concurrent programs are susceptible to lock contention, which leads to low performance and poor scalability. Furthermore, inappropriate granularity of a lock makes lock contention even worse. Compared to coarse-grained lock, fine-grained lock can mitigate lock contention but difficult to use. Converting coarse-grained lock into fine-grained lock manually is not only error-prone and tedious, but also requires a lot of expertise. In this paper, we propose to leverage program analysis techniques and pushdown automaton to automatically covert coarse-grained locks into fine-grained locks to reduce lock contention. We developed a prototype \textit{FineLock} and evaluates it on 5 projects. The evaluation results demonstrate \textit{FineLock} can refactor 1,546 locks in an average of 27.6 seconds, including converting 129 coarse-grained locks into fine-grained locks and 1,417 coarse-grained locks into read/write locks. By automatically providing potential refactoring recommendations, our tool saves a lot of efforts for developers.