An electric power storage device with multiple voltage outputs capable of providing electricity of various voltages for different electronic devices. The device includes a first switch and a second switch that connect to the electronic device; a voltage level-adjusting unit used to output a setting signal of a selected voltage level; a processing unit connecting to the first and second switches and the voltage level-adjusting unit to receive DC electricity and the setting signal to switch on/off the first switch and the second switch after some comparisons and operations; a charging circuit using DC electricity to charge a battery unit; and a voltage transformer connecting respectively to the processing unit, the battery unit, and the second switch to transform electricity obtained from the battery unit under a control of the processing unit and provide the transformed electricity for the electronic device via the second switch.