A computer includes a CPU and a system unit, and further includes a power source, a system driving power generator which converts source power input from the power source to be outputted to the system unit, a CPU driving power generator which outputs driving power to drive the CPU, and a controller which selectively supplies either the source power from the power source or the system power converted from the system driving power generator to an input terminal of the CPU driving power generator according to an operation mode of the CPU. Thus, a computer adjusts a level of power supplied to a CPU driving power generator according to a CPU mode and improves power efficiency, and includes a control method thereof.