  We investigate a relation among neutrino observables, three mixing angles and
two mass squared differences, from a cascade texture of neutrino mass matrix.
We show an allowed region of the correlation by use of current data of neutrino
oscillation experiments. The relation predicts sharp correlations among
neutrino mixing angles as $0.315\lesssim\sin^2\theta_{12}\lesssim0.332$ and
$0.480\lesssim\sin^2\theta_{23}\lesssim0.500$ with a large $\theta_{13}$
($0.03<\sin^22\theta_{13}<0.28$). These magnitudes are modified
$0.310\lesssim\sin^2\theta_{12}\lesssim0.330$ and
$0.540\lesssim\sin^2\theta_{23}\lesssim0.560$ when the charged lepton mass
matrix also has the cascade form.
