Electron cyclotron resonance ion thruster (ECRIT) with a diameter of 10 cm can be operated in multiple types of gases and it is feasible to be applied to air-breathing electric propulsion systems. The study on the neutralizer of the ECRIT running in nitrogen gas is the basis for the study on the ECRIT running in nitrogen-oxygen mixed gas. When the ECR neutralizer of typical 10-cm ECRIT running in xenon gas runs in nitrogen gas, the extracted electron current is reduced, because ions tend to drift out of the neutralizer, due to the lower molecular weight of nitrogen. The typical neutralizer is no longer suitable for running in nitrogen gas. In this work, based on the 10-cm typical ECR neutralizer, in order to inhibit ions drifting out of the neutralizer and improve the performance of electron extraction, a bipolar ECR neutralizer suitable for running in nitrogen gas is experimentally studied. The results show that under the conditions of gas mass flow rate of 0.04 mg/s and input power of 10 W, the anode voltage required by the typical ECR neutralizer running in nitrogen gas is 150 V when the extracted electron current is 134 mA. However, the bipolar ECR neutralizer requires only 50-V anode voltage, which decreases by about 67%. When the anode voltage is 40V, the power loss of the typical ECR neutralizer is 1204.82 W/A, while the power loss of the bipolar ECR neutralizer is 95.23 W/A, which is about 8.3% of the former. The ion shielding effect of the bipolar ECR neutralizer running on nitrogen gas is remarkable and the electron extraction performance is improved.