  We present time-resolved CCD photometry of a dwarf nova NSV 4838 (UMa 8, SDSS
J102320.27+440509.8) during the 2005 June and 2007 February outburst. Both
light curves showed superhumps with a mean period of 0.0699(1) days for the
2005 outburst and 0.069824(83) days for the 2007 outburst, respectively. Using
its known orbital period of 0.0678 days, we estimated the mass ratio of the
system to be $q$=0.13 based on an empirical relation. Although the majority of
SU UMa-type dwarf novae having similar superhump periods show negative period
derivatives, we found that the superhump period increased at $\dot{P}$ /
$P_{\rm sh}$=+7(+3, -4)$\times10^{-5}$ during the 2007 superoutburst. We also
investigated long-term light curves of NSV 4838, from which we derived 340 days
as a supercycle of this system.
