Embodiments of an apparatus and methods for controlling power of a processor having a plurality of cores can independently control individual or selected cores and power supply circuits corresponding to the cores based on, for example, an operation state of the processor or a power mode. Embodiments of an apparatus for controlling power of a processor having a plurality of cores can include a plurality of power supply units each capable of independently supplying a supply power to a plurality of cores provided in one processor, a unit for checking at least one among a use state, a use amount and a power mode of each core and for turning on/off each checked core, and a unit that contacts with the unit for checking for controlling the power supply units in response to an on/off operation of each core.