Core-shell electrocatalyst, in which a Pt monolayer or multilayer shell covers a nano-particle core of a different metal, exhibits high mass activity due to the high utilization of Pt. However, it is still required to improve its durability. If a thermochemically-stable conductive oxide is applied to the core with high durability, such an oxide-core Pt-shell electrocatalyst may exhibit high durability. In this study, we try to realize atomic-level Pt deposition on such a stable oxide to prepare core-shell electrocatalysts, where SnO2 rather than (noble) metals is applied as the core of such electrocatalysts. A photochemical procedure is applied to deposit Pt on SnO2. The dependencies of Pt shell deposition and electrocatalytic activity are analyzed on ultraviolet (UV) irradiation time, suspension temperature during UV irradiation, and the kind and concentration of the sacrificial reagent.