  We report a search result for a light sterile neutrino oscillation with
roughly 2200 live days of data in the RENO experiment. The search is performed
by electron antineutrino ($\overline{\nu}_e$) disappearance taking place
between six 2.8 GW$_{\text{th}}$ reactors and two identical detectors located
at 294 m (near) and 1383 m (far) from the center of reactor array. A spectral
comparison between near and far detectors can explore reactor
$\overline{\nu}_e$ oscillations to a light sterile neutrino. An observed
spectral difference is found to be consistent with that of the three-flavor
oscillation model. This yields limits on $\sin^{2} 2\theta_{14}$ in the
$10^{-4} \lesssim |\Delta m_{41}^2| \lesssim 0.5$ eV$^2$ region, free from
reactor $\overline{\nu}_e$ flux and spectrum uncertainties. The RENO result
provides the most stringent limits on sterile neutrino mixing at $|\Delta
m^2_{41}| \lesssim 0.002$ eV$^2$ using the $\overline{\nu}_e$ disappearance
channel.
