A charging device includes a hand-operated generating circuit, a steady-state voltage circuit electrically connected with the hand-operated generating circuit, a pulse charging circuit electrically connected with the steady-state voltage circuit, a voltage detection circuit electrically connected with the pulse charging circuit, a discharging voltage limiting circuit electrically connected with the pulse charging circuit, a load circuit electrically connected with the discharging voltage limiting circuit and a charging selection circuit electrically connected between the steady-state voltage circuit and the pulse charging circuit. Thus, the charging device can be used to charge an alkaline battery or a common chargeable battery. In addition, the alkaline battery can be replaced when it fails without having to replace the charging device.