  Extending a method developed by Sasaki in the Schwarzschild case and by
Shibata, Sasaki, Tagoshi, and Tanaka in the Kerr case, we calculate the
post-Newtonian expansion of the gravitational wave luminosities from a test
particle in circular orbit around a rotating black hole up to $O(v^8)$ beyond
the quadrupole formula. The orbit of a test particle is restricted on the
equatorial plane. We find that spin dependent terms appear in each
post-Newtonian order, and that at $O(v^6)$ they have a significant effect on
the orbital phase evolution of coalescing compact binaries. By comparing the
post-Newtonian formula of the luminosity with numerical results we find that,
for $30M\lesssim r \lesssim 100M$, the spin dependent terms at $O(v^6)$ and
$O(v^7)$ improve the accuracy of the post-Newtonian formula significantly, but
those at $O(v^8)$ do not improve.
