A thermal detector includes a substrate; a support member supported on the substrate with a cavity interposed therebetween; a heat-detecting element formed on the support member; a first light-absorbing layer formed on the heat-detecting element and the support member so as to be in contact with the heat-detecting element; and a second light-absorbing layer formed on the first light-absorbing layer so as to be in contact with the first light-absorbing layer. The second light-absorbing layer has a higher refractive index than the first light-absorbing layer. A first wavelength resonates between a surface of the support member and an upper surface of the second light-absorbing layer, and a second wavelength, which is different from the first wavelength, resonates between an interface, at which the first light-absorbing layer and the second light-absorbing layer are in contact with each other, and the upper surface of the second light-absorbing layer.