  We successfully grew the high-quality single crystal of
Rb$_{0.78}$Fe$_2$Se$_{1.78}$, which shows sharp superconducting transition in
magnetic susceptibility and electrical resistivity. Resistivity measurements
show the onset superconducting transition ($T_{\rm c}$) at 32.1 K and zero
resistivity at 30 K. From the low-temperature iso-magnetic-field
magnetoresistance, large upper critical field $H_{\rm c2}$(0) has been
estimated as high as 180 T for in-plane field and 59 T for out-of-plane field.
The anisotropy $H^{ab}_{\rm c2}$(0)/$H^{c}_{\rm c2}$(0) is around 3.0, right
lying between those observed in K$_x$Fe$_2$Se$_2$ and Cs$_x$Fe$_2$Se$_2$.
