There is disclosed a diaphragm structure that includes: a ceramic substrate 3 in which at least one opening 2 is formed, and a thin diaphragm portion 4 having a shape protruding on a side opposite to the opening 2 and constituted of a ceramic fired integrally with the ceramic substrate 3 in such a manner as to cover the opening 2. An opening shape of the opening 2 is a shape including at least one tip portion 5 in a longitudinal direction, having a curved shape, and a tapered portion 6 whose opening width gradually narrows toward the tip portion 5 and which is constituted of a curve or a straight line, and a portion of the diaphragm portion 4 corresponding to the tapered portion 6 has such a shape that a protruding height gradually lowers toward the tip portion 5.