In unknown environments, it is highly important to acquire efficiently the map of the unknown environments, which can be realized with swarm robot systems. However, swarm robots suffer from the lack of sensor data due to inevitably limited resources. Then, the individual maps of swarm robots degenerate as time goes, and thus the collective map of merging the individual maps may be inaccurate. This paper presents a feature-based map merging system with mesh networks to acquire individual maps efficiently and merge them accurately. The proposed system was tested with two small robots equipped with relatively low-cost sensors in unknown indoor environments. The experimental results showed that the proposed system acquired successfully individual maps and merged them accurately.