The utility model provides a thickness detecting device, wherein, the device includes: NULL 100, detection electrode 200 and control part 300, control part 300 is connected with NULL 100 for according to the detection information controlled loading of the membrane that the awaits measuring voltage information at NULL 100's voltage, and produce the voltage that voltage information corresponds, wherein, detection information is used for instructing the characteristic of the membrane that awaits measuring, and voltage information is used for instructing the characteristic of the voltage of loading on NULL 100, NULL 100 for the voltage that loading voltage information corresponds, detection electrode 200 corresponds and each other spaced setting with NULL 100, forms monitoring channel between detection electrode 200 and the NULL 100, and detection electrode 200 is used for going up the await measuring thickness of membrane of loaded voltage detecting according to NULL 100, has solved thickness?check's the problem that the accuracy is low in the correlation technique, has improved thickness?check's accuracy.