A solid electrolytic capacitor includes a capacitor element having an anode of a valve action metal, an oxide film layer formed on the surface of the anode, a solid electrolytic layer formed on the oxide film layer and a cathode electrically connected to the solid electrolytic layer, and also a packaging resin formed to cover the capacitor element. An intermediate layer to relieve stress is arranged in at least one part of the interface between the cathode and the packaging resin. The intermediate layer is deformed and/or peels to relieve stress caused by heat applied while mounting the capacitor element on a substrate.