POWER STORAGE DEVICE

An accumulator device which provides a high energy density and high output power is provided. The accumulator device (D) includes a positive electrode in which a positive electrode layer (A) is formed, a negative electrode in which a negative electrode layer (B) is formed, and an electrolytic solution (C). The accumulator device is characterized by satisfying that 1.02 ≤ W/ W≤ 2.08 and that 390 µm ≤ T≤ 750 µm, where Wis the weight of the positive electrode layer (A), Wis the weight of the negative electrode layer (B), and Tis the thickness of the positive electrode in which the positive electrode layer (A) is formed.