We study a very light dilaton, arising from a hidden sector, that couples to the standard model of particle physics. Imposing a scale symmetry below the ultraviolet scale of the standard model, we alleviate the fine-tuning problem associated with Higgs mass. When the electroweak symmetry is spontaneously broken radiatively a la Coleman-Weinberg, the dilaton develops a vacuum expectation value away from the origin to give an extra contribution to the Higgs mass, as a manifestation of the a-theorem in the conformal field theory. The ultraviolet scale of the Higgs field can be naturally much higher than the electroweak scale, as the dilaton drives Higgs mass to the electroweak scale. We also show that the light dilaton in this scenario can be a good candidate of dark matter of mass mD∼1 eV−10 keV, if the ultraviolet scale is about 10−100 TeV.