We investigated the addition of chromium to alumina-supported Pt catalysts and its effect on catalytic activity in methane combustion. The Pt and Cr binary alumina-supported catalysts exhibited much higher activity than those without Cr. Alumina-supported Cr catalysts contain two chromium species, Cr3+ and Cr6+. From XPS analysis, it was found that more Cr6+ species existed in the binary catalysts than in the single alumina-supported Cr catalysts. Pt species in the binary catalysts may promote Cr oxidation. Since Cr6+ species are known to be more active than Cr3+ species in oxidation reactions, the increase in Cr6+ in the binary catalysts may contribute to their higher activity compared with the Pt/Al2O3 catalyst.