The nitrous oxide (N2O) and methane (CH4) emissions were measured from a municipal wastewater treatment plant (WWTP) using a flux chamber to determine the emission factors. The WWTP treats sewage using both the activated-sludge treatment and anaerobic/anoxic/aerobic (A2O) methods. Measurements were performed in the first settling, aeration, and secondary settling basins, as well as in the sludge thickener, sludge digestion tank, and A2O basins. The total emission factors of N2O and CH4 from the activated-sludge treatment were 1.256 g N2O/kg total nitrogen (TN) and 3.734 g CH4/kg biochemical oxygen demand (BOD5), respectively. Those of the advanced treatment (A2O) were 1.605 g N2O/kg TN and 4.022 g CH4/kg BOD5, respectively. These values are applicable as basic data to estimate greenhouse gas emissions.