We theoretically investigate the magnetic-field-angle dependence of the flux-flow resistivity $rho_{rm f}$ in unconventional superconductors. Two contributions to $rho_{rm f}$ are considered: one is the quasiparticle (QP) relaxation time $tau(bm{k}_{rm F})$ and the other is $omega_0(bm{k}_{rm F})$, which is a counterpart to the interlevel spacing of the QP bound states in the quasiclassical approach. Here, $bm{k}_{rm F}$ denotes the position on a Fermi surface. Numerical calculations are conducted for a line-node s-wave and a d-wave pair potential with the same anisotropy of their amplitudes, but with a sign change only for a d-wave one. We show that the field-angle dependence of $rho_{rm f}$ differs prominently between s-wave and d-wave pairs, reflecting the phase of the pair potentials. We also discuss the case where $tau$ is constant and compare it with the more general case where $tau$ depends on $bm{k}_{rm F}$.
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