  We obtained new upper limits on the diffuse gamma rays from the inner
Galactic (IG) and outer Galactic (OG) planes in 3.10 TeV region, using the
Tibet air shower data and new Monte Carlo simulation results. A difference of
the effective area of the air-shower array for observing gamma rays and cosmic
rays was carefully taken into account in this analysis, resulting in that the
flux upper limits of the diffuse TeV gamma rays were reduced by factors of
4.0.3.7 for 3.10 TeV than those in our previous results (Amenomori, M., Ayabe,
S., Cui, S.W., et al. Observation of multi-TeV diffuse gamma rays from the
Galactic plane with the Tibet air shower array. Astrophys. J. 580, 887.895,
2002.). This new result suggests that the inverse power index of the energy
spectrum of source electrons responsible for generating diffuse TeV gamma rays
through inverse Compton effect should be steeper than 2.2 and 2.1 for IG and OG
planes, respectively, with 99%C.L.
