  We numerically investigate the effect of in-plane anisotropic Fermi surface
(FS) on the flux-flow resistivity $\rho_{\rm f}$ under rotating magnetic field
on the basis of the quasiclassical Green's function method. We demonstrate that
one can detect the phase in pairing potential of Cooper pair through the
field-angular dependence of $\rho_{\rm f}$ even if the FS has in-plane
anisotropy. In addition, we point out one can detect the gap-node directions
irrespective of the FS anisotropy by measuring $\rho_{\rm f}$ under rotating
field.
