When a temperature difference is locally generated by a small heated sphere in liquid, natural convection occurs, and largely affects the temperature and velocity fields. However, a transient temperature field during natural convection in such a small region has never been directly measured. In this study, using the temperature imaging method based on the temperature dependence of the absorption band of water in the near-infrared region, we investigated the natural convection around a 1-mm-dimater magnetic sphere heated inductively. By applying the inverse Abel transform to the absorbance profile along each horizontal line in the image acquired by this method, three-dimensional axisymmetric distributions of the absorption coefficient were obtained, and converted to those of the temperature. The results revealed the evolution of the temperature field to the thermal plume induced by natural convection. Furthermore, these results were verified by comparison with numerical simulation results.