  We present the results of the high-resolution spectroscopy of the FU
Orionis-type star V960 Mon. The brightness of V960 Mon decreased continuously
after the outburst was detected in 2014 November. During this dimming event, we
have carried out medium-resolution spectroscopic monitoring observations and
found that the equivalent width of the absorption features showed variations.
To further investigate the spectroscopic variations, we conducted a
high-resolution spectroscopic observation of V960 Mon with the Subaru Telescope
and the High Dispersion Spectrograph on 2018 January 8 and 2020 February 1. By
comparing this spectrum with the archival data of the Keck Observatory and the
High Resolution Echelle Spectrometer taken between 2014 and 2017, we found that
the absorption profiles changed as V960 Mon faded. The line profile of
absorption lines such as Fe I and Ca I can be explained by a sum of the spectra
of the disk atmosphere and the central star. The model spectrum created to
explain the variations of the line profiles suggests that the effective
temperature of the central star is $\sim$5500 K, which is comparable to that of
the pre-outburst phase with a distance of 1.6 kpc with Gaia. The spectrum also
shows that the effective temperature of the disk atmosphere decreased as V960
Mon faded. The variations of the H$\alpha$ and Ca II lines (8498.0 A, 8542.1 A)
also show that the V960 Mon spectrum became central-star dominant.
