We introduce the concepts of harmonic stability and harmonic index for a co
mplete minimal hypersurface in Rn+1 (n greater than or equal to 3) and prov
e that the hypersurface has only finitely many ends if its harmonic index i
s finite. Furthermore, the number of ends is bounded from above by I plus t
he harmonic index. Each end has a representation of nonnegative harmonic fu
nction, and these,functions form a partition of unity. We also give an expl
icit estimate of the harmonic index for a class of special minimal hypersur
faces, namely, minimal hypersurfaces with finite total scalar curvature. It
is shown that for such a submanifold the space of bounded harmonic functio
ns is exactly generated by the representation functions of the ends.