  We comprehensively investigate a chaotic inflation model proposed recently in
the framework of supergravity. In this model, the form of K\"ahler potential is
determined by a symmetry, that is, the Nambu-Goldstone-like shift symmetry,
which guarantees the absence of the exponential factor in the potential for the
inflaton field. Though we need the introduction of small parameters, the
smallness of the parameters is justified also by symmetries. That is, the zero
limit of the small parameters recovers symmetries, which is natural in the 't
Hooft's sense. The leptogenesis scenario via the inflaton decay in this chaotic
inflation model is also discussed. We find that the lepton asymmetry enough to
explain the present baryon number density is produced for low reheating
temperatures avoiding the overproduction of gravitinos.
