The present invention provides a secondary battery, a battery unit and a battery module. The secondary battery includes a battery device that has a thickness of 3 to 20 mm, and a battery discharge capacity of 3 to 50 Ah, and an exterior material that packages the battery device. The battery device includes a positive electrode that has a positive electrode current collector and a positive electrode active material layer, a negative electrode that has a negative electrode current collector and a negative electrode active material layer, a separator that is interposed between the positive electrode and the negative electrode that are alternately laminated, a positive electrode tab that is electrically connected to a positive electrode current collector exposed portion and is led-out to the outside of the exterior material, and a negative electrode tab that is electrically connected to a negative electrode current collector exposed portion and is led-out to the outside of the exterior material.