  The gauge theory on $M_4\times Z_2$ geometry is applied to the
Brans-Dicke(BD) theory, where $M_4$ is the four dimensional space-time and
$Z_2$ is a discrete space with two points. This approach had been previously
proposed by Konisi and Saito without recourse to noncommutative geometry(NCG).
Since our approach is geometrically simpler and clearer than NCG, one can see
more directly the effect of the $Z_2$ space in obtaining the BD theory.
