  We study the evolution of the universe which contains a multiple number of
non-relativistic scalar fields decaying into both radiation and pressureless
matter. We present a powerful analytic formalism to calculate the matter and
radiation curvature perturbations, and find that our analytic estimates agree
with full numerical results within an error of less than one percent. Also we
discuss the isocurvature perturbation between matter and radiation components,
which may be detected by near future cosmological observations, and point out
that it crucially depends on the branching ratio of the decay rate of the
scalar fields and that it is hard to make any model independent predictions.
