  In this paper, we show that in the framework of chaotic braneworld inflation,
after preheating, the remaining oscillating inflaton field can play the role of
dark matter with the observed level. Augmented by a non-zero effective
cosmological constant $\Lambda_4$ on the brane, triple unification of
inflation, dark matter and dark energy by a single field is realized. Our model
perhaps is the simplest one in the market of theories to achieve triple
unification.
