We obtained near-infrared spectroscopy of the z =5.74 QSO , SDSSp J104433.04-012502.2 with the Infrared Camera and Spectrograph of the Subaru telescope .
The redshift of 5.74 corresponds to a cosmological age of 1.0 Gyr for the current \Lambda -dominated cosmology .
We found a similar strength of the Fe \emissiontype II ( 3000-3500 Å ) emission lines in SDSSp J104433.04-012502.2 as in low redshift QSOs .
This is the highest redshift detection of iron .
We subtracted a power-law continuum from the spectrum and fitted model Fe \emissiontype II emission and Balmer continuum .
The rest equivalent width of Fe \emissiontype II ( 3000-3500 Å ) is \sim 30 Å which is similar to those of low redshift QSOs measured by the same manner .
The chemical enrichment models that assume the life time of the progenitor of SNe Ia is longer than 1 Gyr predict that weaker Fe \emissiontype II emission than low redshift .
However , none of the observed high redshift ( z > 3 ) QSOs show a systematic decrease of Fe \emissiontype II emission compared with low redshift QSOs .
This may due to a shorter lifetime of SNe Ia in QSO nuclei than in the solar neighborhood .
Another reason of strong Fe \emissiontype II emission at z = 5.74 may be longer cosmological age due to smaller \Omega _ { M } .