A chemical-vapor-deposition (CVD) technique operated under atmospheric pressure is available to synthesize metal oxide crystals with various morphologies. This CVD technique provides highly supersaturating conditions that induce morphological instability of growing crystallites. In this study, the metal oxide material with rock salt structure was selected to confirm the possibility of whisker growth of the cubic system crystal. The MgO whiskers grew epitaxially on the single crystalline substrate of (0001) sapphire under appropriate conditions. The MgO whiskers were also formed epitaxially on the top of the ZnO whiskers. The unique whisker with the MgO/ZnO hetero-junction was successfully obtained.