A producing method of a power storage device includes roll pressing a mixture laminated portion of a wide strip-shaped electrode plate, non-laminated-portion stretching of stretching a pair of mixture non-laminated portions of the wide strip-shaped electrode plate in a longitudinal direction, laminated-portion stretching of stretching a pair of mixture non-laminated-portion-side sections of the mixture laminated portion located on the mixture non-laminated portion side, cutting the wide strip-shaped electrode plate at a center of a width direction in the longitudinal direction to divide into two strip-shaped electrode plates, winding up the two strip-shaped electrode plates around winding cores with applying tensile force in the longitudinal direction in a roll-like shape to form electrode rolls, and storing each of the electrode rolls.