A single spin-rotational state-selected [(J, M)＝(2, 2)] O2 beam allows us to investigate how the molecular alignment and electron spin affect oxygen chemisorption. Recent experiments of O2 chemisorption on magnetized Ni(111) have indicated that O2 sticking probability is higher when its spin is oriented anti-parallel to the majority spin direction of the Ni substrate. The spin dependence becomes more significant at lower translational energy, and amounts to over 40% at thermal energy. This clear spin effect suggests that incident O2 molecules keep high spin polarizations even at the position of the dissociation barrier. In this article, the observed spin effect is reviewed after introducing the spinrotational state of O2 (3Σg-).