A battery system includes a battery circuit group in which a plurality of battery circuits, each including a plurality of battery units including a battery and a switching unit connected in series, are connected in parallel, and a control unit that controls the switching unit. The switching unit switches a state of the battery unit between a first state, in which the battery is connected between a positive electrode end and a negative electrode end of the battery unit, and a second state, in which the positive electrode end and the negative electrode end are connected without the battery. When discharging, the control unit controls the switching unit such that the state of the battery unit including the battery determined to be not fully discharged becomes the first state, and the state of the battery unit including the battery determined to be fully discharged becomes the second state.