  We have measured the magnetic susceptibility of single-crystal
Cu_{1-x}Ni_xGeO_3 to study doping effects of the magnetic impurity (Ni^{2+} has
S=1 spin) on the inorganic spin-Peierls (SP) material CuGeO_3. We observed the
disappearance of the SP transition and the abrupt increase of the Neel
temperature from 2.5 to 3.4 K at x nearly equal to 0.020, which indicates the
first-order phase transition between the dimerized-antiferromagnetic (D-AF) and
the uniform-antiferromagnetic (U-AF) phases, as was discovered in Mg-doped
(Mg^{2+} is nonmagnetic) system [T. Masuda et al., Phys. Rev. Lett. 80, 4566
(1998)]. This indicates that this transition is universal for the doping to Cu
site. We also found another phase with the easy axis in the a-c plane in low x
region.
