  It has been proved in \cite{LS} that cluster variables in cluster algebras of
every skew-symmetric cluster algebra are positive. We prove that any regular
generalized cluster variable of an affine quiver is positive. As a corollary,
we obtain that generalized cluster variables of affine quivers are positive and
construct various positive bases. This generalizes the results in \cite{Dupont}
and \cite{DXX}.
