  This article is concerned with the study of the holonomy group of flat
solvmanifolds. It is known that the holonomy group of a flat solvmanifold is
abelian; we give an elementary proof of this fact and moreover we prove that
any finite abelian group is the holonomy group of a flat solvmanifold.
Furthermore, we show that the minimal dimension of a flat solvmanifold with
holonomy group $\mathbb{Z}_n$ coincides with the minimal dimension of a compact
flat manifold with holonomy group $\mathbb{Z}_n$. Finally, we give the possible
holonomy groups of flat solvmanifolds in dimensions 3, 4, 5 and 6; exhibiting
in the latter case a general construction to show examples of non cyclic
holonomy groups.
