  We have measured the temperature dependence of resistivity in
single-crystalline CeNiGe$_{3}$ under hydrostatic pressure in order to
establish the characteristic pressure-temperature phase diagram. The transition
temperature to AFM-I phase $T_{\rm N1}$ = 5.5 K at ambient pressure initially
increases with increasing pressure and has a maximum at $\sim$ 3.0 GPa. Above
2.3 GPa, a clear zero-resistivity is observed (SC-I phase) and this
superconducting (SC) state coexists with AFM-I phase. The SC-I phase suddenly
disappears at 3.7 GPa simultaneously with the appearance of an additional kink
anomaly corresponding to the phase transition to AFM-II phase. The AFM-II phase
is continuously suppressed with further increasing pressure and disappears at
$\sim$ 6.5 GPa. In the narrow range near the critical pressure, an SC phase
reappears (SC-II phase). A large initial slope of upper critical field
$\mu_0H_{\rm c2}$ and non-Fermi liquid behavior indicate that the SC-II phase
is mediated by antiferromagnetic fluctuations. On the other hand, the robust
coexistence of the SC-I phase and AFM-I phase is unusual on the contrary to
superconductivity near a quantum critical point on most of heavy-fermion
compounds.
