  Three dimensional Thirring model with $N$ four-component Dirac fermions,
reformulated as a lattice gauge theory, is studied by computer simulation.
According to an $8^{3}$ data and preliminary $16^3$ data, chiral symmetry is
found to be spontaneously broken for $N=2,\;4$ and 6. $N=2$ data exhibits long
tail of the non-vanishing chiral condensate into weak coupling region, and
$N=6$ case shows phase separation between the strong coupling region and the
weak coupling region. Although the comparison between $8^3$ data and $16^3$
data shows large finite volume effects, an existence of the critical fermion
flavor number $N_{{\rm cr}}$ $(2<N_{{\rm cr}}<6)$ for which the chiral behavior
changes its character, is suggested by the current numerical data.
