Abstract: A pressure sensor 1 comprises a metallic housing 10 having a space 18 communicated to a pressure detection space and a thin rising portion 17 formed on the upper end of the peripheral area, a sensor element 20, a sensor element holder 30, a metallic pressure case 60 having a ceiling portion 61, and a connector case 70 formed of an insulating material, wherein a collar portion 211 of a base plate 21 of the sensor element 20 including a pressure sensing element 22 is contacted to an annular protrusion 33 positioned around the opening 32 of the sensor element holder 30, and the collar portion 211 is airtightly welded to the annular protrusion 33 by projection welding. Further, the collar portion 63 on the pressure case 60 and the peak surface 35 of the holder 30 is airtightly welded by an electron beam welding. The airtight interior space defined by the sensor element 20, the sensor element holder 30 and the pressure case 60 is utilized as the reference pressure space.