A composite body of the present invention includes a base and an oxide layer arranged on the base, the oxide layer containing more than 45% by volume of a perovskite-type oxide phase. The composite body may include a first member, a second member, and a joining portion that joins the first member and the second member, at least one of the first member and the second member serving as the base, and the joining portion serving as the oxide layer. The composite body may include the base and a covering portion that covers the whole or part of a surface of the base, the covering portion being formed of the oxide layer.