A sensor including a carrier having two channels, a capacitive sensing element disposed on the carrier, and a cover is provided. The capacitive sensing element has a membrane, and a first chamber is formed between the membrane and the carrier. The cover is disposed on the carrier for covering the capacitive sensing element. A second chamber is formed between the membrane and the cover. The first chamber and the second chamber are located at two sides of the membrane, and the channels are respectively communicated with the first chamber and the second chamber.