Topology optimization is an advanced design method for generating lightweight and high-performance structures by determination of the material distribution. One of important drawbacks of the topology optimization, especially performed by the density-based approach, is that distinct and smooth boundaries cannot be directly obtained owing to checkerboard patterns, grayscales and irregular shapes. This drawback make it difficult to manufacture the results of topology optimization. In this paper, a novel methodology is proposed to automatically obtain optimal smooth boundaries of topology optimization results using an efficient boundary smoothing technique and H¹ gradient method, which is a node-based parameter-free optimization method. With this methodology, distinct and smooth optimal boundaries can be determined without any shape design parameterization. Moreover, re-mesh is not necessary in the shape updating process and the process is fully automatic. The validity and practical utility of this method is verified through a numerical example with respect to a mean compliance minimization problem.