A solid electrolyte assembly includes a substrate, a first electrode layer, and a solid electrolyte layer, wherein the first electrode layer and the solid electrolyte layer are stacked in this order on one face of the substrate. The first electrode layer includes: platinum or the like; and a metal oxide having ion conductivity. The substrate has a plurality of through-holes (hole portions) extending in a direction that intersects a face of the substrate that is opposed to the first electrode layer. The metal oxide preferably has oxide ion conductivity. The metal oxide preferably includes one or more rare earths.