  The cosmological perturbation theory is revisited from the holographic point
of view. In the case of the single brane model, it turns out that the AdS/CFT
correspondence plays an important role. In the case of the two-brane model, it
is shown that the effective equations of motion becomes the quasi-scalar-tensor
gravity. It is also demonstrated that the radion anisotropy gives the CMB
fluctuations through the Sachs-Wolfe effect.
