  In the context of the dual superconductor picture for the confinement
mechanism, we study maximally Abelian (MA) projection of quark confinement in
SU(3) quenched lattice QCD with $32^4$ at $\beta$=6.4 (i.e., $a \simeq$ 0.058
fm). We investigate the static quark-antiquark potential $V(r)$, its Abelian
part $V_{\rm Abel}(r)$ and its off-diagonal part $V_{\rm off}(r)$,
respectively, from the on-axis lattice data. As a remarkable fact, we find
almost perfect Abelian dominance for quark confinement, i.e., $\sigma_{\rm
Abel} \simeq \sigma$ for the string tension, on the fine and large-volume
lattice. We find also a nontrivial summation relation of $V(r) \simeq V_{\rm
Abel}(r) + V_{\rm off}(r)$.
