A membrane circuit board includes a first membrane substrate, a spacer substrate, a second membrane substrate and a third membrane substrate. The first membrane substrate includes a first gas channel and a first conductive contact. The spacer substrate includes a first gas hole and a second gas hole. The second membrane substrate includes a second gas channel, a second conductive contact, a third gas hole and a fourth gas hole. The second gas channel is in communication with the third gas hole and the fourth gas hole. The second gas channel is in communication with the first gas channel through the first gas hole and the second gas hole. The third membrane substrate includes a third gas channel. The third gas channel is in communication with the second gas channel through the third gas hole and the fourth gas hole.