A reduction-oxidation sensor device and a manufacturing method thereof are provided. The reduction-oxidation sensor device includes a first electrode, at least one sensing structure and a second electrode. The first electrode is located on a substrate. The at least one sensing structure is located on the first electrode and the substrate. The at least one sensing structure includes a metal nanowire layer and a metal oxide layer. The metal nanowire layer is disposed on the first electrode and the substrate. The metal nanowire layer is wrapped by the metal oxide layer. The second electrode is located on the at least one sensing structure.