We investigated the Ru 4d and O 2p electronic structure and magnetic properties of an ultrahigh-quality SrRuO3 film on SrTiO3 grown by machine-learning assisted molecular-beam epitaxy. The high itinerancy and long quantum lifetimes of the quasiparticles in the Ru 4d t(2g)-O 2p hybridized valence band are confirmed by observing the prominent well-screened peak in the Ru 3d core-level photoemission spectrum, the coherent peak near the Fermi energy in the valence-band spectrum, and quantum oscillations in the resistivity. The element-specific magnetic properties and the hybridization between the Ru 4d and O 2p orbitals were characterized by Ru M-2,M-3-edge and O K-edge soft x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements. The ultrahigh-quality SrRuO3 film with the residual resistivity ratio of 86 shows the large orbital magnetic moment of oxygen ions induced by the strong orbital hybridization of the O 2p states with the spin-polarized Ru 4d t(2g) states. The film also shows single-domain perpendicular magnetization with an almost ideal remanent magnetization ratio of 0.97. These results provide detailed insights into the relevance between orbital hybridization and the perpendicular magnetic anisotropy in SrRuO3/SrTiO3 systems.