Geographic routing is one of the most effective routing methods for ad-hoc wireless networks, and each node selects the forwarding node to the destination node by using position information of its neighbor nodes. However, it has a problem that forwarded packets may encounter the void area where no closer node to the destination is. In this paper, we propose a geographic routing method with landmarks between source and destination node, called GLGR (Grid Landmark-based Geographic Routing). To handle node mobility, our proposed method employs grid-based landmarks, not node-based landmarks used in the traditional methods. A grid is a divided region of communication area and its position is static. Therefore, landmarks can keep the appropriate position to forward data packets to the destination, especially in the case that the void is static. Also, to adaptively change the cache interval of landmark information, the node guesses whether the encountered void is static or dynamic by using the node habitability of grids. Network simulation results about packet arrival rate and end-to-end delay showed 30% better performance of our proposed method than the traditional methods in the best case, with suppressing control overhead.