A pressure sensor includes: a housing; a pressure input orifice opened at a pipe sleeve of the housing; a diaphragm sealing the pressure input orifice, the diaphragm having a first surface serving as a pressure receiving surface; a pressure sensitive unit using a direction of detecting a force as a detecting axis. A first end of the pressure sensitive unit is connected to a central area of a second surface of the diaphragm. A second end of the pressure sensitive unit is connected to the housing. The detecting axis is approximately orthogonal to the pressure receiving surface. A circumference of a portion where the central area and the first end of the pressure sensitive unit are in contact with each other is located inside a circumference of the central area. A thickness of the central area is larger than a thickness of an area surrounding the central area.