  We have studied Ni-substitution effect in LaFe$_{1-x}$Ni$_{x}$AsO ($0\leq x
\leq0.1$) by the measurements of x-ray diffraction, electrical resistivity,
magnetic susceptibility, and heat capacity. The nickel doping drastically
suppresses the resistivity anomaly associated with spin-density-wave ordering
in the parent compound. Superconductivity emerges in a narrow region of
$0.03\leq x \leq0.06$ with the maximum $T_c$ of 6.5 K at $x$=0.04, where
enhanced magnetic susceptibility shows up. The upper critical field at zero
temperature is estimated to exceed the Pauli paramagnetic limit. The much
lowered $T_c$ in comparison with LaFeAsO$_{1-x}$F$_{x}$ system is discussed.
