A power management apparatus cooperates with a controlled apparatus and is electrically connected to a power system. The power management apparatus includes an energy storing module, a switching module and a comparing module. The energy storing module is electrically connected to the controlled apparatus, and the switching module is electrically connected to the energy storing module. The comparing module is electrically connected to the switching module and receives a detection signal. The comparing module generates a periodic signal to control the switching module according to the detection signal. The energy storing module stores an electric energy during a cycle of the periodic signal and releases the electric energy during other cycle after the said cycle. Thereby, the power management apparatus is capable of effectively protecting the controlled apparatus, avoiding the waste of the power, and storing and using extra power.