  We report a $^{71}$Ga nuclear-quadrupole-resonance (NQR) study on the
characteristics of superconductivity in noncentrosymmetric Ir$_2$Ga$_9$ at zero
field (H=0). The $^{71}$Ga-NQR measurements have revealed that $1/T_1$ has the
clear coherence peak just below $T_{\rm c}$, and decreases exponentially upon
further cooling in Ir$_2$Ga$_9$. From these results, Ir$_2$Ga$_9$ is concluded
to be the conventional s-wave superconductor. Despite the lack of spatial
centrosymmetry, there are no evidence for unconventional superconducting state
ascribed to ASOC in Ir$_2$Ga$_9$.
