  The seesaw model of quark masses is studied systematically, focusing on its
developments. A framework allowing the top quark mass to be of the order of the
electroweak symmetry breaking scale, while the remaining light quarks have much
smaller masses, due to the seesaw mechanism, is presented. The violation of the
GIM mechanism is shown to be small and the tree level FCNC are suppressed
naturally. In this model, there are many particles which could contribute to
the FCNC in the one-loop level. Parameters of the model are constrained by
using the experimental data on K^0-\bar{K}^0 mixing and \epsilon_K. The rare K
meson decays K_{L,S} -> \pi^0 \nu \bar{\nu} and K^+ -> \pi^+ \nu \bar{\nu} are
also investigated in the model. In these processes the scalar operators
(\bar{s}d)(\bar{\nu}_{\tau}\nu_{\tau}), which are derived from box diagrams in
the model, play an important role due to an enhancement factor M_K/m_s in the
matrix element <\pi|\bar{s}d|K>. It is emphasized that the K_L decay process
through the scalar operator is not the CP violating mode, so B(K_L -> \pi^0 \nu
\bar{\nu}) remains non-zero even in the CP conserved limit. The pion energy
spectra for these processes are predicted.
