  The purpose of this paper is to present our study on the restoration of the
Lorentz symmetry for a Lifshitz-type scalar theory in the infrared region by
using nonperturbative methods. We apply the Wegner-Houghton equation, which is
one of the exact renormalization group equations, to the Lifshitz-type theory.
Analyzing the equation for a z=2, d=3+1 Lifshitz-type scalar model, and using
some variable transformations, we found that broken symmetry terms vanish in
the infrared region. This shows that the Lifshitz-type scalar model dynamically
restores the Lorentz symmetry at low energy. Our result provides a definition
of ultraviolet complete renormalizable scalar field theories. These theories
can have nontrivial interaction terms of \phi^{n} (n=4, 6, 8, 10) even when the
Lorentz symmetry is restored at low energy.
