  We present details of simulations for the light hadron spectrum in quenched
QCD carried out on the CP-PACS parallel computer. Simulations are made with the
Wilson quark action and the plaquette gauge action on 32^3x56 - 64^3x112
lattices at four lattice spacings (a \approx 0.1-0.05 fm) and the spatial
extent of 3 fm. Hadronic observables are calculated at five quark masses
(m_{PS}/m_V \approx 0.75 - 0.4), assuming the u and d quarks being degenerate
but treating the s quark separately. We find that the presence of quenched
chiral singularities is supported from an analysis of the pseudoscalar meson
data. We take m_\pi, m_\rho and m_K (or m_\phi) as input. After chiral and
continuum extrapolations, the agreement of the calculated mass spectrum with
experiment is at a 10% level. In comparison with the statistical accuracy of
1-3% and systematic errors of at most 1.7% we have achieved, this demonstrates
a failure of the quenched approximation for the hadron spectrum: the meson
hyperfine splitting is too small, and the octet masses and the decuplet mass
splittings are both smaller than experiment. Light quark masses are calculated
using two definitions: the conventional one and the one based on the
axial-vector Ward identity. The two results converge toward the continuum
limit, yielding m_{ud}=4.29(14)^{+0.51}_{-0.79} MeV. The s quark mass depends
on the strange hadron mass chosen for input: m_s = 113.8(2.3)^{+5.8}_{-2.9} MeV
from m_K and m_s = 142.3(5.8)^{+22.0}_{-0} MeV from m_\phi, indicating again a
failure of the quenched approximation. We obtain \Lambda_{\bar{MS}}^{(0)}=
219.5(5.4) MeV. An O(10%) deviation from experiment is observed in the
pseudoscalar meson decay constants.
