  We investigate the negative-parity baryon spectra in quenched lattice QCD. We
employ the anisotropic lattice with standard Wilson gauge and O(a) improved
Wilson quark actions at three values of lattice spacings with renormalized
anisotropy xi=a_sigma/a_tau=4, where a_sigma and a_tau are spatial and temporal
lattice spacings, respectively. The negative-parity baryons are measured with
the parity projection. In particular, we pay much attention to the lowest SU(3)
flavor-singlet negative-parity baryon, which is assigned as the Lambda(1405) in
the quark model. For the flavor octet and decuplet negative-parity baryons, the
calculated masses are close to the experimental values of corresponding
lowest-lying negative-parity baryons. In contrast, the flavor-singlet baryon is
found to be about 1.7 GeV, which is much heavier than the Lambda(1405).
Therefore, it is difficult to identify the Lambda(1405) to be the
flavor-singlet three-quark state, which seems to support an interesting picture
of the penta-quark (uds qbar q) state or the N-Kbar molecule for the
Lambda(1405).
