To prevent a battery pack from being over-discharged even under a state that the battery pack (a secondary battery) is connected to a discharging device that is not connected to an ac input power source for a long time. A charging device has a pair of output lines and an anode terminal and a cathode terminal of a secondary battery electrically connected between the output lines to carry out a charging operation. In the charging device including a component circuit part electrically connected by traversing a part between the pair of output lines, a switching element is inserted between the component circuit part and one of the pair of output lines. When the charging device is not connected to an input power source, the switching element is allowed to be non-conductive to interrupt a discharging path so that the component circuit part does not form the discharging path.