  We have investigated the electrical resistivity of the heavy fermion
superconductor PrOs$_{4}$Sb$_{12}$ in the mixed state. We found unusual double
minima in the flux-flow resistivity as a function of magnetic field below the
upper critical field for the first time, indicating double peaks in the pinning
force density ($F_{\rm P}$). Estimated $F_{\rm P}$ at the peak exhibits
apparent dependence on applied field direction; composed of two-fold and
four-fold symmetries mimicking the reported angular dependence of thermal
conductivity ($\kappa$). The result is discussed in correlation with the double
step superconducting (SC) transition in the specific heat and the multiple
SC-phases inferred from the angular dependence of $\kappa$.
