A pressure sensor including a housing extending along an axial line, a diaphragm fixed to a front-end side of the housing, a piezoelectric unit disposed in a hole in the housing and including a piezoelectric element, a transmission member that transmits deformation of the diaphragm to the piezoelectric unit, and a guide member having a through hole extending along the axial line and surrounding the piezoelectric unit in the through hole. (SL/AL)≤0.26 is satisfied in the cross section perpendicular to the axial line passing through the piezoelectric element, where SL is the maximum value of the distance in the radial direction between the center of the through hole and the center of the piezoelectric element and AL is the maximum value of the distance in the radial direction between the outside surface of the piezoelectric element and the center of the through hole.