The Namsan Ecological Tower Site based on a flux tower was equipped with eddy covariance and automatic opening/closing chamber systems to collect long-term continuous measurements of $CO_2$ flux, such as the net ecosystem exchange (NEE) and soil $CO_2$ efflux in a cool-temperate Quercus mongolica forest. The mean concentrations of atmospheric $CO_2$ ($705;mg/m^3$) during the summer were smaller than those measured ($770;mg/m^3$) during the winter. The mean $CO_2$ flux during the summer period was negative ($-0.34;mg;m^{-2};s^{-1}$), while that during the winter period was positive ($0.14;mg;m^{-2};s^{-1}$). $CO_2$ was deposited from the atmosphere to the surface in the summer. The daily mean value of soil $CO_2$ efflux increased from spring to summer. The seasonal pattern in the rate of soil $CO_2$ efflux tightly followed the seasonal pattern in soil temperatures. The $Q_{10}$ values for soil $CO_2$ efflux varied in a range from 2.12 to 3.26, and increased with increasing soil depth. The maximum value of total carbon uptake (i.e., NEE) during the growing season was $-8;g;CO_2m^{-2};day^{-1}$. At the same time, the rate of soil $CO_2$ efflux was $6.9;g;CO_2m^{-2};day^{-1}$. The amplitude of flux variations in NEE was approximately 14% larger than those in soil $CO_2$ efflux. These results suggest that in cool-temperate regions of the Korean peninsula, the forest ecosystem of Q. mongolica may have a larger atmospheric $CO_2$ uptake, due primarily to its high photosynthetic capacity and low ecosystem respiration.