A non-invasive carbon dioxide sensor includes a conductive substrate, a electrical transmission layer, and a gas sensing layer. The conductive substrate includes a base and at least two electrode disposed on the base and spaced apart from each other. The electrical transmission layer is disposed on the conductive substrate, and includes a plurality of carbon nanotubes crossing one another and a plurality of metal oxide nanorods attached to the carbon nanotubes. The carbon nanotubes and the metal oxide nanorods together form a composite material having a hierarchical three-dimensional structure. The gas sensing layer is disposed on the electrical transmission layer and includes a polymer material that contains at least one amino functional group capable of reacting with carbon dioxide. A method for manufacturing a non-invasive carbon dioxide sensor is also provided |