The present study investigated the nitrogen balance in swine manure composting to evaluate the effect of nitrite () accumulation, which induces nitrogenous emissions, such as N2O, during compost maturation. During active composting, most N losses result from NH3 emission, which was 9.5% of the initial total nitrogen (TNinitial), after which, began to accumulate as only ammonia-oxidizing bacteria proliferated. After active composting, the addition of mature swine compost (MSC), including nitrite-oxidizing bacteria (NOB), could prevent accumulation and reduce N2O emission by 70% compared with the control in which accumulated as a result of delayed growth of indigenous NOB. Total N2O emissions in the control and in the treatment of MSC addition (MA) were 9.3% and 3.0% of TNinitial, respectively, whereas N losses as the sum total of NH3 and N2O over the whole period were 19.0% (control) and 12.8% (MA) of TNinitial, respectively. However, the difference in total N losses was markedly greater than that measured as NH3 and N2O, which were 27.8% (control) and 13.3% (MA) of TNinitial, respectively. These results demonstrated that the magnitude of nitrogen losses induced by accumulation is too large to ignore in the composting of swine manure.