The paper gives a sufficient condition for a quantale to be isomorphic to a sub-quantale of the quantale whose elements are binary relations on a set and whose order and monoid structure are respectively given by inclusion and relational composition and the identity relation. A quantale has such a relational representation, if its underlying lattice is a powerset of some set. We also show some other equivalent conditions of the sufficient condition. © 2012 Springer-Verlag.