We theoretically investigate the surface orientation dependence of band alignments and dipole formation at 4H-SiC/SiO₂ interfaces on the basis of first-principles calculations. The calculations demonstrate that the offsets of valence and conduction bands depends on the orientation and chemical bonds at the interface. The conduction band offset on the Si-face interface is larger than those on the C-face and m-face interfaces. Furthermore, it is found that the dipole formation due to Si-O and C-O bonds significantly changes the band structure of 4H-SiC, resulting in large conduction bands offset. The formation of Si-O bond at the interface is of importance for obtaining large conduction band offset, leading to higher reliability in SiC metal-oxide-semiconductor field-effect transistors.