A GaInNAs alloy on GaAs substrate has been very promising for long-wavelength vertical-cavity surface-emitting lasers (VCSELs) as an active layer. In spite of many groups reported the excellent temperature characteristics of the threshold current of the GaInNAs/GaAs edge-emitting lasers, discussions of the temperature dependence of the lasing characteristics except threshold current is few. In this paper, temperature characteristics of GaInNAs lasers grown by chemical beam epitaxy (CBE) emitting at λ=1.27 µm and λ=1.30 µm were investigated in detail. The characteristic temperature (T0) ranging from 10 to 80 varies from 60 to 130 K and decreased with decreasing cavity length for shorter cavity (< 400 µm) devices. On the other hand, longer cavity (< 400 µm) devices show that the cavity length does not affect so much to T0. The internal losses did not increase with increasing temperature. On the other hand, internal quantum efficiencies decreased with increasing temperature. It is considered that non-radiative recombination center with large temperature dependence may influence the decrease of the internal quantum efficiency due to the insufficient crystal quality of GaInNAs layer. The transparency current densities were unchanged for all temperature range, however, the gain constants decreased with increasing temperature. Thus, the decrease of the gain constant is considered to be due to decreasing of gain. Unchanged both transparency current density and internal loss may also express that these temperature characteristics were not induced by carrier overflow but be done by decreasing of the gain. From the results, it is considered that the temperature dependence of the gain originated from the Fermi-Dirac distribution of carriers was dominant for the temperature characteristics of GaInNAs/GaAs lasers. Due to the temperature dependence on the gain, the T0 decreases with increasing mirror loss.