From the viewpoint of rational homotopy theory, we introduce an iterated cyclic homology of connected commutative differential graded algebras over the rational number field, which is regarded as a generalization of the ordinary cyclic homology. Let T be the circle group and $\mathcal F$ (Tl, X) denote the function space of continuous maps from the l-dimensional torus Tl to an l-connected space X. It is also shown that the iterated cyclic homology of the differential graded algebra of polynomial forms on X is isomorphic to the rational cohomology algebra of the Borel space ET × T $\mathcal F$ (Tl, X), where the T-action on $\mathcal F$ (Tl, X) is induced by the diagonal action of T on the source space Tl.