Nitrogen‐doped carbon materials exhibit a catalytic activity, such as an oxygen reduction reaction (ORR). In this study, we performed nitrogen doping on a carbon nanoballoon (CNB), which is a nanometer‐sized carbon particle in the form of a hollow sphere made of graphite by radiofrequency (RF) magnetron plasma in a gas mixture of nitrogen and helium. Nitrogen‐doped CNBs (N‐doped CNBs) were prepared by different plasma irradiation conditions: the sample installation positions, input powers, and irradiation times. The samples were examined for chemical state by X‐ray photoelectron spectroscopy (XPS). Hydrodynamic voltammetry was used for the evaluation of the catalytic activity of a N‐doped CNB with a pyridinic N concentration of 0.4‐1.0 at.%. As a result, the onset potential was measured to be 0.13 V versus RHE (reversible hydrogen electrode), which was close to the previously reported data of highly oriented pyrolytic graphite (HOPG) with a pyridinic N concentration of 0.57 at.%, which was prepared by annealing under NH3. [ABSTRACT FROM AUTHOR]