A glow plug with a pressure sensor, comprising: a cylindrical metal shell having an axial hole extending in an axial line direction; a cylindrical metallic outer cylinder having an outer cylinder hole inner part arranged in the axial hole of the metal shell, and an outer cylinder projection part projecting toward a front end side in the axial line direction from a front end of the metal shell; a bar-shaped ceramic heater made of ceramics, held by the outer cylinder, having a heater front end part projecting toward the front end side in the axial line direction from a front end of the outer cylinder, and held by the metal shell to be displaceable in the axial line direction together with the outer cylinder; and a sensor unit configured to sense displacement of the ceramic heater, wherein the outer cylinder hole inner part of the outer cylinder has a heater holding part holding the ceramic heater therein, and the outer cylinder projection part of the outer cylinder surrounds the ceramic heater provided therein in a loose-fit manner, the glow plug further comprising a cylindrical metallic holding member arranged in the axial hole, held by the metal shell, and holding the outer cylinder and the ceramic heater therein to allow the displacement, wherein the outer cylinder hole inner part of the outer cylinder has a heater spacing part spaced apart from the ceramic heater provided therein on at least one of the front end side and a rear end side of the heater holding part in the axial line direction, and the holding member is welded to the heater spacing part of the outer cylinder hole inner part of the outer cylinder. a cylindrical metal shell having an axial hole extending in an axial line direction; a cylindrical metallic outer cylinder having an outer cylinder hole inner part arranged in the axial hole of the metal shell, and an outer cylinder projection part projecting toward a front end side in the axial line direction from a front end of the metal shell; a bar-shaped ceramic heater made of ceramics, held by the outer cylinder, having a heater front end part projecting toward the front end side in the axial line direction from a front end of the outer cylinder, and held by the metal shell to be displaceable in the axial line direction together with the outer cylinder; and a sensor unit configured to sense displacement of the ceramic heater, wherein the outer cylinder hole inner part of the outer cylinder has a heater holding part holding the ceramic heater therein, and the outer cylinder projection part of the outer cylinder surrounds the ceramic heater provided therein in a loose-fit manner, the glow plug further comprising a cylindrical metallic holding member arranged in the axial hole, held by the metal shell, and holding the outer cylinder and the ceramic heater therein to allow the displacement, wherein the outer cylinder hole inner part of the outer cylinder has a heater spacing part spaced apart from the ceramic heater provided therein on at least one of the front end side and a rear end side of the heater holding part in the axial line direction, and the holding member is welded to the heater spacing part of the outer cylinder hole inner part of the outer cylinder.