An electronic apparatus and a power controlling method thereof are provided. The electronic apparatus includes a system unit supplied with power to conduct an operation, and a power supply unit including a power control unit controlling output of standby power, and supplying the standby power to the system unit. The power control unit includes a pulse width modulation (PWM) generation unit generating a PWM signal and a first switching unit switched on/off based on an external input signal to selectively supply power to the PWM generation unit. Thus, power consumption of the electronic apparatus in the standby mode is minimized to facilitate conformance with power regulations in accordance with an energy saving policy.