The present invention provides an extension card incorporating a power management device applicable to electronic devices. During the operating process, if the removal of the top cover from the housing of the electronic device is detected, power supply to the electronic device is immediately cut off. The extension card incorporating the power management device is characterized in that a plurality of signal pins are disposed on a side of the power management device and electrically connected to a plurality of idle pins of the extension card, the idle pins conveying no signals processed by the extension card but transmitting a power-off signal to the motherboard when electrically connected to the connecting port of the motherboard.