The energy band alignment of the atomic-layer-deposited In2O3/β-Ga2O3 ( 2 ¯ 01) interface is evaluated by X-ray photoelectron spectroscopy. The X-ray diffraction pattern reveals that the In2O3 film grown at 160 °C is amorphous, while it becomes polycrystalline at a higher deposition temperature of 200 °C. The bandgaps, determined by reflection electron energy loss spectroscopy, are 4.65, 3.85, and 3.47 eV for β-Ga2O3, polycrystalline In2O3, and amorphous In2O3, respectively. Both amorphous and polycrystalline In2O3/β-Ga2O3 interfaces have Type I alignment. The conduction and valence band offsets at the polycrystalline (amorphous) In2O3/β-Ga2O3 interface are 0.35 and 0.45 eV (0.39 and 0.79 eV), respectively. These observations suggest that polycrystalline In2O3 as an intermediate semiconductor layer is beneficial to the barrier reduction of metal/Ga2O3 contact.