Abstract: The RENO experiment has observed the disappearance of reactor electron antineutrinos, consistent with neutrino oscillations, with a significance of 4.9 standard deviations. Antineutrinos from six reactors at Yonggwang Nuclear Power Plant in Korea, are detected by two identical detectors located at 294 m and 1383 m, respectively, from the reactor array center. In the 229 day data-taking period of 11 August 2011 to 26 March 2012, the far (near) detector observed 17102 (154088) electron antineutrino candidate events with a background fraction of 5.5% (2.7%). A ratio of observed to expected number of antineutrinos in the far detector is 0.920+-0.009(stat.)+-0.014(syst.). From the deficit, we find sin^2(2theta_13)=0.113+-0.013(stat.)+-0.019(syst,) based on a rate-only analysis. In this talk, its detailed analysis will be presented.