We have prepared sodium-doped C60 utilizing the thermal decomposition of sodium azide (NaN3). The strong low-Magnetic field microwave absorption with a clear hysteresis was observed in the samples of NanC60 (n=3-4), indicating the superconducting nature. By means of a SQUID measurement, the superconducting transition temperature is found to be around 12 K. Significantly, elemental analysis detected a nitrogen which was surely produced in the process of die thermal decomposition of NaN3. We suppose that this new superconducting phase will be NaxNyC60 where x is between 3 and 4, and y is unknown. This is the first superconducting material in Na-doped C60 without other alkali metals.