  In this article, we define the tensor product $V\otimes W$ of a
representation $V$ of a quiver $Q$ with a representation $W$ of an another
quiver $Q'$, and show that the representation $V\otimes W$ is semistable if $V$
and $W$ are semistable. Over the field of complex numbers, we also describe a
relation between the natural line bundles, and between the universal
representations on the fine moduli spaces $N_1, N_2$ and $N_3$ of
representations of $Q, Q'$ and $Q\otimes Q'$ respectively. We then prove that
the internal product $\tilde{Q}\otimes \tilde{Q'}$ of covering quivers is a
sub-quiver of the covering quiver $\widetilde{Q\otimes Q'}$. We deduce the
relation between stability of the representations $\widetilde{V\otimes W}$ and
$\tilde{V} \otimes \tilde{W}$. We also lift the relation between natural line
bundles on the product of moduli spaces $\tilde{N_1} \times \tilde{N_2}$.
