A method for scaling a dynamic voltage of a CPU is achieved by setting a voltage setting point for each of a plurality of code segments of a program, and profiling workload by measuring a workload variation of each of the code segments based on data that changes whenever measured, selecting a plurality of combinations, each having a plurality of voltage setting points, and calculating workload estimators corresponding to the voltage setting points of each of the selected combinations based on the workload variation measured in the workload profiling operation, selecting an optimal combination that consumes a least energy of the CPU based on the workload estimators, and determining whether a real time constraint is satisfied when an operating voltage is set based on the workload estimator corresponding to each of the voltage setting points of the optimal combination during runtime, and setting the operating voltage based on a result of the determination.