A pressure sensor generates an electrical output according to a fluid pressure in a detection space applied to a diaphragm. The diaphragm is flexibly deformable in a thickness direction. The pressure sensor includes a pressure receiving recess defining the detection space and a protection film covering the pressure receiving recess. The protection film has a corner portion provided in an inner corner area of the pressure receiving recess and a thin film portion having a uniform thickness. The corner portion is located outside the diaphragm in an in-plane direction orthogonal to the thickness direction.