MANETs (Mobile Ad-hoc NETworks) have been studied for a long time to provide multi-hop wireless communications among temporarily gathered mobile devices. However, due to the nature of wireless communications, the communication performance of a flow is easily degraded by even a single local congestion on the path. A simple solution for this problem is to utilize detour paths that avoid the congested area. However, to provide detour paths that avoid the area whenever a packet faces congestion is in fact a challenging task because the detour paths must avoid relatively large region in which harmful radio waves interfere. In this paper, we propose a routing scheme that proactively computes detour paths to avoid the congested area ahead of packets. Specifically, when a packet meets congestion, we assume that the next-next-hop node along the shortest path to the destination is the center of the congestion, and forward the packet to its destination without visiting the node neighboring the congestion central node. We designed an algorithm that builds the secondary routing tables that works to provide the detour paths on top of the distributed link-state routing scheme.