  We theoretically investigate the quasiparticle scattering rate $\varGamma$
inside a vortex core in the existence of non-magnetic impurities distributed
randomly in a superconductor. We show that the dependence of $\varGamma$ on the
magnetic field direction is sensitive to the sign of the pair potential. The
behavior of $\varGamma$ is quite different between an s-wave and a d-wave pair
potential, where these are assumed to have the same amplitude anisotropy, but a
sign change only for the d-wave one. It is suggested that measurements of the
microwave surface impedance with changing applied-field directions would be
used for the phase-sensitive identification of pairing symmetry.
