  We report the out-of-plane resistivity in the systematically
oxygen-controlled single crystals
Bi$_{1.74}$Pb$_{0.38}$Sr$_{1.88}$CuO$_{6+\delta}$ in magnetic fields parallel
to the c-axis. Two characteristic temperatures $T^*$ and $T^{**}$ are found at
which a semiconductor-like upturn starts to develop and the magnetoresistance
changes its sign from positive to negative at lower temperature, respectively.
The obtained phase diagram strongly suggests that the pseudogap temperature
correlating to the superconducting gap is not $T^{*}$ but $T^{**}$. The gap
opened at $T^*$ may relate to another phenomenon with the different energy
scale such as the antiferromagnetic excitation due to the exchange interaction
between Cu$^{2+}$ spins.
