In an evaluation method, voltages at ends of a to-be-measured capacitor and a capacitance-adjustable circuit are switched in response to a first set of clock signals so as to adjust an integrated voltage to be a sum of the integrated voltage and a first difference voltage. Next, whether a first control event is received is judged. If not, the previous step is performed. If yes, an integration operation is performed to switch a voltage of an end of a known capacitor in order to adjust the integrated voltage to be a sum of the integrated voltage and a second difference voltage. Next, whether an integrating period ends is judged. If not, the first step is repeated. If yes, a capacitance of the to-be-measured capacitor is obtained according to the number of times that the integration operation is performed in the integrating period and a capacitance of the known capacitor.