A diaphragm is arranged on the upper surface of a silicon substrate so as to cover a chamber in the silicon substrate. Multiple anchors are provided on the upper surface of the silicon substrate, and the lower surfaces of corner portions of the diaphragm are supported by the anchors. Also, a fixed electrode plate is provided above the diaphragm with an air gap therebetween. In a view from a direction perpendicular to the upper surface of the silicon substrate, the entire length of the outer edge of the diaphragm located between adjacent anchors is located outward of a line segment that circumscribes the edges of the adjacent anchors on the side distant from the center of the diaphragm. Also, one or two or more through-holes are formed in the diaphragm in the vicinity of the anchors.