A power-saving electronic device for use with a computer motherboard in a “suspend to memory” state is disclosed. The power-saving electronic device enables compulsory interruption of power supply to a south bridge chip and a super input output (SIO) chip of the computer motherboard in the “suspend to memory” state, such as an S3 state of Advanced Configuration and Power Interface (ACPI), so as to save power. After a user presses a power switch, the power-saving electronic device enables the south bridge chip and SIO chip to be powered on by a standby power supplied thereto and enables the computer motherboard to remain capable of awakening and resuming from the S3 state.