A damper system for a vehicle which is mounted on the vehicle and which comprises an electromagnetic damper configured to generate a damping force with respect to a motion of a sprung portion and an unsprung portion toward each other and a motion thereof away from each other, wherein the electromagnetic damper includes: an electromagnetic motor; a motion converting mechanism configured to convert the motions of the sprung portion and the unsprung portion toward and away from each other into a motion of the electromagnetic motor and vice versa; and an external circuit disposed outside the electromagnetic motor and including a first connection passage in which an electric current is allowed to flow from a first terminal as one of two terminals of the electromagnetic motor to a second terminal as the other of the two terminals while an electric current is prohibited from flowing from the second terminal to the first terminal and a second connection passage which is provided separately from the first connection passage and in which the electric current is allowed to flow from the second terminal to the first terminal of the electromagnetic motor while the electric current is prohibited from flowing from the first terminal to the second terminal, wherein the electromagnetic damper is configured to generate the damping force that depends on an electromotive force of the electromagnetic motor, with respect to the motion of the sprung portion and the unsprung portion toward each other by permitting a generated current by the electromagnetic motor to flow through the first connection passage and with respect to the motion of the sprung portion the unsprung portion away from each other by permitting the generated current by the electromagnetic motor to flow through the second connection passage, characterized in that the external circuit includes: a battery-device connection circuit which is provided separately from the first connection passage and the second connection passage and which is configured to selectively establish: (i) a first state in which the first terminal of the electromagnetic motor and a high-potential-side terminal of a battery device mounted on the vehicle are electrically connected and the second terminal of the electromagnetic motor and a low-potential-side terminal of the battery device are electrically connected while the first terminal and the low-potential-side terminal are not electrically connected and the second terminal and the high-potential-side terminal are not electrically connected; and ii) a second state in which the second terminal and the high-potential-side terminal are electrically connected and the first terminal and the low-potential-side terminal are electrically connected while the first terminal and the high-potential-side terminal are not electrically connected and the second terminal and the low-potential-side terminal are not electrically connected; and a battery-device-connection-circuit-current adjuster (108, 114, 122, 144) configured to adjust an electric current that flows in the battery-device connection circuit, wherein the damper system comprises an external-circuit controller configured to control an electric current that flows in the electromagnetic motor by controlling the external circuit, and wherein the external-circuit controller is configured to control a flow of an electric current between the battery device and the electromagnetic motor by controlling the battery-device-connection-circuit-current adjuster. an electromagnetic motor; a motion converting mechanism configured to convert the motions of the sprung portion and the unsprung portion toward and away from each other into a motion of the electromagnetic motor and vice versa; and an external circuit disposed outside the electromagnetic motor and including a first connection passage in which an electric current is allowed to flow from a first terminal as one of two terminals of the electromagnetic motor to a second terminal as the other of the two terminals while an electric current is prohibited from flowing from the second terminal to the first terminal and a second connection passage which is provided separately from the first connection passage and in which the electric current is allowed to flow from the second terminal to the first terminal of the electromagnetic motor while the electric current is prohibited from flowing from the first terminal to the second terminal, a battery-device connection circuit which is provided separately from the first connection passage and the second connection passage and which is configured to selectively establish: (i) a first state in which the first terminal of the electromagnetic motor and a high-potential-side terminal of a battery device mounted on the vehicle are electrically connected and the second terminal of the electromagnetic motor and a low-potential-side terminal of the battery device are electrically connected while the first terminal and the low-potential-side terminal are not electrically connected and the second terminal and the high-potential-side terminal are not electrically connected; and ii) a second state in which the second terminal and the high-potential-side terminal are electrically connected and the first terminal and the low-potential-side terminal are electrically connected while the first terminal and the high-potential-side terminal are not electrically connected and the second terminal and the low-potential-side terminal are not electrically connected; and a battery-device-connection-circuit-current adjuster (108, 114, 122, 144) configured to adjust an electric current that flows in the battery-device connection circuit,