  The charmonium and bottomonium mass spectra are investigated in potential
nonrelativistic QCD (pNRQCD) with the heavy quark potential computed by lattice
QCD simulations. The potential consists of a static potential and relativistic
corrections classified in powers of the inverse of heavy quark mass m, and the
effects of the O(1/m) and O(1/m^{2}) spin-orbit corrections on the mass spectra
are examined systematically. The pattern of the mass spectra is found to be in
fairly good agreement with experimental data, in which the O(1/m) correction
gives an important contribution.
