Disclosed is a capacitive touch detecting device including a sampler circuit and a detection-and-calibration circuit. The sampler circuit executes the following steps: charging a capacitor when the level of a clock signal is high, wherein the capacitor's capacitance is a first capacitance provided a touch event occurs and is a second capacitance provided the touch event doesn't occur, the first capacitance is greater than the second capacitance and related to a parasitic capacitance and a touch capacitance, and the second capacitance is unrelated to the touch capacitance; sampling a voltage determined by the capacitor during the level transition of the clock signal to generate a sample value; and discharging the capacitor when the level of the clock signal is low. The detection-and-calibration circuit determines whether the touch event occurs and whether at least one parameter needs to be updated according to the sample value and at least one parameter.