  Gravitino problem is discussed in detail. We derive an upperbound on the
reheating temperature from the constraints of the big-bang nucleosynthesis and
the present mass density of the universe. Compared to previous works, we have
improve the following three points; (i) the gravitino production cross sections
are calculated by taking all the relevant terms in the supergravity lagrangian
into account, (ii) high energy photon spectrum is obtained by solving the
Boltzmann equations numerically, and (iii) the evolutions of the light elements
(D, T, $^3$He, $^4$He) at the temperature lower than $\sim$1MeV are calculated
by using modified Kawano's computer code.
