  We provide the geometrical meaning of the ${\cal N}=4$ superconformal index.
With this interpretation, the ${\cal N}=4$ superconformal index can be realized
as the partition function on a Scherk-Schwarz deformed background. We apply the
localization method in TQFT to compute the deformed partition function since
the deformed action can be written as a $\delta_\epsilon$-exact form. The
critical points of the deformed action turn out to be the space of flat
connections which are, in fact, zero modes of the gauge field. The one-loop
evaluation over the space of flat connections reduces to the matrix integral by
which the ${\cal N}=4$ superconformal index is expressed.
