An optical device includes a joining structure in which a first conductive film (110) and a second conductive film (130) are joined to each other. The first conductive film (110), which constitutes the joining structure, is constituted by a transparent conductive material and the like. The second conductive film (130), which constitutes the joining structure, is constituted by a metal material. A dispersing agent, which is constituted by a material different from the transparent conductive material, exists at a portion of the first conductive film (110) which is located at the periphery of the second conductive film (130).