  We investigate the electronic states of a one-dimensional two-orbital Hubbard
model with band splitting by the exact diagonalization method. The Luttinger
liquid parameter $K_{\rho}$ is calculated to obtain superconducting (SC) phase
diagram as a function of on-site interactions: the intra- and inter-orbital
Coulomb $U$ and $U'$, the Hund coupling $J$, and the pair transfer $J'$. In
this model, electron and hole Fermi pockets are produced when the Fermi level
crosses both the upper and lower orbital bands. We find that the system shows
two types of SC phases, the SC \Roman{u'-large} for $U>U'$ and the SC
\Roman{u-large} for $U<U'$, in the wide parameter region including both weak
and strong correlation regimes. Pairing correlation functions indicate that the
most dominant pairing for the SC \Roman{u'-large} (SC \Roman{u-large}) is the
intersite (on-site) intraorbital spin-singlet with (without) sign reversal of
the order parameters between two Fermi pockets. The result of the SC
\Roman{u'-large} is consistent with the sign-reversing s-wave pairing that has
recently been proposed for iron oxypnictide superconductors.
