Based on the monthly weather report of Korea Meteorological Administration (KMA) and daily sea surface temperature (SST) in Incheon harbor of National Fisheries Research and Development Institute, heat budget in Incheon coastal area was estimated. The temperature differences between the sea surface and near bottom were nearly within 1℃. This indicate the mixing from the sea surface and the bottom. The net heat flux through the sea surface and the advection through the inner and outer bay was affected uniformly to the water body in Incheon coastal area. The net heat flux was about 110W/㎡ in maximum value on May, about -80W/㎡ in minimum on January. The net heat flux through the sea surface from the solar radiation was about 2.35 × 10^5W during the year. This heat flux flew out the bay through the advection by the same flux.