In this study, we report the development of an absolute determination method based on potential-controlled coulometric analysis using carbon-felt-electrode-introduced nitrogen-containing functional groups fabricated by the electrode oxidation of ammonium carbamate solution for measuring nitrite. The potential-controlled coulometric cell was constructed by using a working electrode consisting of a carbon felt electrode that was electro-oxidized at +1.1 V (vs Ag/AgCl) in 0.1 M ammonium carbamate solution. When the applied potential of the sensor cell was +0.75 V, the oxidized current of nitrite was immediately observed by adding 10 µL of 1 mM nitrite. In addition, the electron number of the electrode reaction was two electron paths from the estimation of the electrical charge of nitrite detection. This finding indicates that the proposed determination method resulted in the absolute quantity analysis of nitrite. The current vs time curves indicate that the determination of nitrite was finished completely in a relatively short time (~30 s). The relative standard deviation (RSD) for ten successive measurements of 1 mM nitrite was 2.2%. This indicates that our coulometric method can be used for the absolute determination of the nitrite concentration in practical applications.