Disclosed are a method for fabricating a quantum dot. The method includes the steps of (a) preparing a compound semiconductor layer including a quantum well structure formed by sequentially stacking a first barrier layer, a well layer and a second barrier layer; (b) forming a dielectric thin film pattern including a first dielectric thin film having a thermal expansion coefficient higher than a thermal expansion coefficient of the second barrier layer and a second dielectric thin film having a thermal expansion coefficient lower than the thermal expansion coefficient of the second barrier layer on the second barrier layer; and (c) heat-treating the compound semiconductor layer formed thereon with the dielectric thin film pattern to cause an intermixing between elements of the well layer and elements of the barrier layers at a region of the compound semiconductor layer under the second dielectric thin film.