  Recently the existence of a random critical line in two dimensional Dirac
fermions is confirmed. In this paper, we focus on its scaling properties,
especially in the critical region. We treat Dirac fermions in two dimensions
with two types of randomness, a random site (RS) model and a random hopping
(RH) model. The RS model belongs to the usual orthogonal class and all states
are localized. For the RH model, there is an additional symmetry expressed by
${\{}{\cal H},{\gamma}{\}}=0$. Therefore, although all non-zero energy states
localize, the localization length diverges at the zero energy. In the weak
localization region, the generalized Ohm's law in fractional dimensions,
$d^{*}(<2)$, has been observed for the RH model.
