A storage device includes: a first conductive layer; a second conductive layer; and a resistance-variable layer disposed between the first conductive layer and the second conductive layer, and including a first chalcogenide containing a first element which is either silicon or germanium. An insulating layer is disposed in a second direction perpendicular to a first direction from the first conductive layer to the second conductive layer with respect to the resistance-variable layer. A first region is disposed between the resistance-variable layer and the insulating layer, and has a third concentration of the first element higher than both a first concentration of the first element in the resistance-variable layer and a second concentration of the first element in the insulating layer.