A power adapter apparatus and a power management method thereof are disclosed in the invention. The power adapter includes an output interface and a power modulation unit. The power adapter can be electrically connected with an electronic device through the output interface. There is a detective structure disposed on the output interface. The power management method includes steps of: 1) detecting whether the power adapter apparatus is electrically connected with the electronic device by the detective structure; and 2) when the output interface is detected to be disconnected from the electronic device, switching the power modulation unit to a standby state, so as to reduce a total power consumption of the power modulation unit.