  There is mounting evidence that neutrinos undergo fast flavor conversion
(FFC) in core-collapse supernova (CCSN). In this letter, we investigate the
roles of stellar rotation on the occurrence of FFC by carrying out axisymmetric
CCSN simulations with full Boltzmann neutrino transport. Our result suggests
that electron neutrino lepton number (ELN) angular crossings, which are the
necessary and sufficient condition to trigger FFC, preferably occur in the
equatorial region for rotating CCSNe. By scrutinizing the neutrino--matter
interaction and neutrino radiation field, we find some pieces of evidence that
the stellar rotation facilitates the occurrence of FFC. The
low-electron-fraction region in the post-shock layer expands by centrifugal
force, enhancing the disparity of neutrino absorption between electron-type
neutrinos ($\nu_{\rm e}$) and their anti-particles ($\bar{\nu}_{\rm e}$). This
has a significant impact on the angular distribution of neutrinos in momentum
space, in which $\nu_{\rm e}$ tends to be more isotropic than $\bar{\nu}_{\rm
e}$; consequently, ELN crossings emerge. The ELN crossing found in this study
is clearly associated with rotation, which motivates further investigation on
how the subsequent FFC influences explosion dynamics, nucleosynthesis, and
neutrino signals in rotating CCSNe.
