A power tracking device and a power tracking method is disclosed herein. The power tracking device includes a power voltage setting circuit, a switch, a switching signal circuit, and a voltage memory circuit. The switching signal circuit is configured for sending a first control signal to the switch. When the switch receives the first control signal and electrically isolates the power source and the power voltage setting circuit, the voltage memory circuit stores an open circuit voltage of the power source and sends a setting voltage relative to the open circuit voltage, and when the switch receives the first control signal and electrically connects the power source and the power voltage setting circuit, the power voltage setting circuit sets an output voltage of the power source to correspond with the setting voltage.