A computer device and frequency adjusting method for central processing unit are provided. The computer device including a CPU, a voltage regulator module, a clock generator, a power-on module, a chip set and an embedded controller. The power-on module activates the voltage regulator module, the clock generator and the CPU respectively. The voltage regulator module provides the operating voltage of the CPU. The clock generator provides the operating clock of the CPU. Before the CPU is activated, the embedded controller adjusts the operating clock and the operating voltage provided from the clock generator and the voltage regulator module the CPU, the CPU performs overclocking/downclocking directly by using the adjusted operating clock and the adjusted operating voltage after the CPU is activated.