The structure of Euiseong Sub-basin and boundary of sub-basins were examined by analytical aeromagentci anomaly data. Magnetic lineaments have trends of NE-SW, NWW-SEE and NEE-SWW. The NE-SW lineaments in the sedimentary formations and pre-Cretaceous basement are assoicated with the direction of expansion of basin and the lineaments in the volcanic rocks and intrusives indicate the direction of structural weakness ones such as fault, which were major gateways of igneous activities. Euiseong Subbasin is bounded by pre-existing Andong Fault, pre-Cretaceous basement in the west, NE-SW lineament from Jyungsan to Angang, and NW-SE lineament connecting southwestern boundary of Palgongsan Granite and Jeokje Fault. In particular , the NW-SE lineament , which caused upheavel of pre-Cretaceous rocks, on Jeokje Fault is inferred as a boundary between Euiseong and Milyang Sub-basins.