The current study analyzed the home range size of the Common Kestrel (Falco tinnunculus) by observation using the natural markings in the suburban area of Busan from December 2009 to May 2010. In all, 26 individual kestrels were observed in the study area, of which 14 individual kestrels were frequently observed (more than five times) and 12 were observed less frequently (less than five times). Mean home range sizes of the 14 frequently observed kestrels were estimated using two different methods (minimum convex polygon (MCP) method and fixed kernel (FK) method): 34.49 ㏊(2.74–163.96 ㏊) by 100% MCP, 41.35 ㏊(3.54– 99.02 ㏊) by the 95% FK, 14.33 ㏊(0.20-31.57 ㏊) by the 75% FK and 5.75 ㏊(0.52–14.74 ㏊) by the 50% FK. The mean home range size was larger for males than for females estimated at 51.50 ㏊(15.04–163.96 ㏊) and 11.80㏊(2.74–24.48 ㏊), respectively, by the 100 % MCP method and 8.02 ㏊(2.38–14.74 ㏊) and 2.72 ㏊ (0.52–4.28 ㏊), respectively, by the 50 % Fixed Kernel method. The home range sizes by sexes in breeding pairs differed during the wintering and breeding seasons; the sizes decreased among females but increased among males during the breeding season. Such differences of home range sizes between sexes could be attributed to parental role division during the breeding season. Females stay in the nest or next to it during laying, incubating, and feeding activities, and males go far away from their nest sites to forage areas for their fledglings for most of the breeding period.