A frequency adjusting apparatus used in a processing chip operated at an operation frequency according to a power is provided that includes a clock supplying circuit, a frequency division circuit and a control circuit. The clock supplying circuit outputs one of clock signals as a supplied clock signal. The frequency division circuit performs frequency division on the supplied clock signal according to a parameter to generate an output clock signal. The control circuit determines a combination of a selected clock signal and a value of the parameter for gradually increasing the frequency of the output clock signal during the increasing of the voltage value that passes through voltage value sections, wherein when the voltage value is determined to be larger than a second threshold value and when the voltage value sections correspond to higher voltage values, the selected clock signal has a higher frequency.