There is provided an interposer which meets the need of improving electrical reliability of an electronic device. An interposer includes a substrate including a penetrating-hole in a thickness direction thereof, and a penetrating conductor disposed in the penetrating-hole. The substrate includes a first insulating layer and a second inorganic insulating layer which are separated from each other in the thickness direction, and a first resin layer interposed between the first inorganic insulating layer and the second inorganic insulating layer and being in contact with the first inorganic insulating layer and the second inorganic insulating layer. A coefficient of thermal expansion of the first resin layer in thickness and planar directions thereof is larger than those of the first inorganic insulating layer and the second inorganic insulating layer.