A microphone unit includes first and second diaphragms; a substrate on a top surface of which are installed the first and second diaphragms; and a cover disposed covering the first and second diaphragms, the cover joined to an outside edge of the substrate and forming an internal space. There are formed in the substrate first and second openings that are formed respectively in the top and bottom surfaces of the substrate, and an internal sound path communicating from the first opening to the second opening. The first diaphragm is disposed on the substrate so as to cover and hide the first opening. The second diaphragm is disposed so as to seal off a partial region away from the first opening of the top surface of the substrate. A third opening is formed in the cover, and the internal space communicates to an outside space via the third opening.