  Lattice QCD should allow quantitative predictions for the heavy quark physics
from first principles. Up to now, however, most approaches have based on the
nonrelativistic effective theory, with which the continuum limit can not be
taken in principle. In this paper we investigate feasibility of relativistic
approaches to the heavy quark physics in lattice QCD. We first examine validity
of the idea that the use of the anisotropic lattice could be advantageous to
control the $m_Q a$ corrections. Our perturbative calculation, however, reveals
that this is not true. We instead propose a new relativistic approach to handle
heavy quarks on the isotropic lattice. We explain how power corrections of $m_Q
a$ can be avoided and remaining uncertainties are reduced to be of order
$(a\Lambda_{QCD})^2$.
