A joined structure which is configured such that a space between adjacent substrates is filled with a filling material. The joined structure includes a first substrate having a first conductor formed on a surface of the first substrate, a second substrate having a second conductor formed on a surface of the second substrate, arranged so that a surface of the first substrate faces a surface of the second substrate, a connecting conductor which electrically connects the first conductor and the second conductor, and a filling material between the first substrate and the second substrate. The filling material is formed into such a shape that a space is provided which corresponds to at least one of the first conductor, the second and the connecting conductor.