  The finite temperature transition or crossover in QCD with two degenerate
Wilson quarks is investigated using a renormalization group improved action. At
$\beta=2.0$ and 2.1 where $a^{-1} \sim 1.0-1.2$ GeV, the expectation value of
the Polyakov loop and the pion screening mass on an $8^3 \times 4$ lattice vary
smoothly with the hopping parameter through the transition/crossover. The quark
screening mass in the high temperature phase agrees well with that in the low
temperature phase calculated on an $8^4$ lattice. The smooth transition of the
observables is totally different from the sharp transition found for the
standard action at $\beta=5.0$ and 5.1 where $a^{-1}$ is also $1.0-1.2$ GeV.
