Power saving device capable of automatically sensing standby current

The invention discloses a power saving device capable of automatically sensing standby current, which is used in a power device such as a power outlet or other power supply devices for giving the power device ability of electricity saving. When the power saving device normally works, a threshold current setting unit of a controlling and processing module is configured to automatically calculate a threshold current based on current signals sensed by a current detecting unit under different operation modes of at least one electrical device electrically connected to the power device. Moreover, when at least one standby current sensed from the electrical device is determined to be lower than the threshold current, the controlling and processing module immediately switches a switch unit to an open-circuit state, thereby causing the electrical device unable to receive electricity from the power device. Consequently, the power device exhibits the ability of power saving.