Doppler-free two-photon excitation spectra and the Zeeman effects for the 1(0)(1)14(0)(1) band of the S-1 B-1(2u) <- S-0 (1)A(1g) transition in gaseous benzene-d(6) were measured. Although the spectral lines were strongly perturbed, almost all of the lines near the band origin could be assigned. From a deperturbation analysis, the perturbation near the band origin was identified as originating from an anharmonic resonance interaction. Perturbation centered at K = 28-29 in the 14(0)(1) band was analyzed, and it was identified as originating from a perpendicular Coriolis interaction. The symmetry and the assignment of the perturbing state proposed by Schubert et al. (Schubert, U.; Riedle, E.; Neusser, H. J. J. Chem. Phys. 1989, 90, 5994.) were confirmed. No perturbation originating from an interaction with a triplet state was observed in both bands. From the Zeeman spectra and the analysis, it is demonstrated that rotationally resolved levels are not mixed with a triplet state. The intersystem mixing is not likely to occur at levels of low excess energy in the S-1 state of an isolated benzene. Nonradiative decay of an isolated benzene in the low vibronic levels of the S-1 state will occur through the internal mixing followed by the rotational and vibrational relaxation in the S-0 state.