An object is to provide a winding-type electric age device capable of preventing swaying or movement of an electrode assembly. Provided is a winding-type electric storage device with a flat electrode assembly, which includes a core, and a case in which the electrode assembly is housed, the core including first and second curved sections which are disposed so that the inner circumferential surfaces thereof face to each other, and each of which is at least in part composed of a material stacked into two or more plies, and first and second opposed sections which connect the mutually-opposed first ends and second ends of the first and second curved sections to each other.