A new superconducting sodium cobalt oxide (see figure, left) has been synthesized through soft-chemical modification using alpha-NaCoO2 as a parent compund, in place of the gamma-Na0.7CoC2 used to make the first cobalt oxide superconductor (see figure, right). A three-layer periodicity of the CoO2 stacking sequence exists in the present material, in contrast to a two-layer one in the previous. The new oxide has a superconducting transition at 4.6 K.