Recently, research has been actively conducted to determine the surrounding environment for autonomous driving of autonomous vehicles or mobile robots. Therefore, it is important to determine the correct driving environment. In this paper, the region growing technique is applied to 3D point cloud data to detect movable area. By the proposed method, the real-time detection of movable areas is possible. In addition, the experimental results are presented by comparing the ground truth 2D grid map with the detected movable area.