A pressure sensor comprising a sensor module, comprising an open end through which a fluid to be measured is introduced, and a diaphragm displaceable in accordance with a pressure of the fluid to be measured introduced through the open end; and a joint attached to the sensor module and comprising an introduction port through which the fluid to be measured is introduced to the sensor module, wherein the sensor module and the joint are made of different metal materials, the sensor module comprises: a first portion and a second portion, the first portion comprising: the diaphragm; a cylindrical portion connected to an outer peripheral portion of the diaphragm; and a small-diameter portion connected to the cylindrical portion, and the second portion comprising a large-diameter portion connected to the small-diameter portion and having a larger diameter than a diameter of the small-diameter portion, the open end is formed in the large-diameter portion, whereby the cylindrical portion, the small-diameter portion and the large-diameter portion are between the diaphragm and the open end, a step with which a peripheral edge of the large-diameter portion is engaged is provided in the joint, the large-diameter portion is bonded to the joint through a bonding portion, the bonding portion is formed between an outer circumferential portion of the large-diameter portion and the joint, where a part of the outer circumferential portion of the large-diameter portion and an inner circumferential portion of the joint are bonded by plastic deformation bonding to keep a connection in the axial direction, characterized by a space configured to prevent a stress caused on the joint when the joint and the large-diameter portion are bonded from being transmitted to the diaphragm is provided between the joint and the first portion. a sensor module, comprising an open end through which a fluid to be measured is introduced, and a diaphragm displaceable in accordance with a pressure of the fluid to be measured introduced through the open end; and a joint attached to the sensor module and comprising an introduction port through which the fluid to be measured is introduced to the sensor module, wherein the sensor module and the joint are made of different metal materials, the sensor module comprises: a first portion and a second portion, the first portion comprising: the diaphragm; a cylindrical portion connected to an outer peripheral portion of the diaphragm; and a small-diameter portion connected to the cylindrical portion, and the second portion comprising a large-diameter portion connected to the small-diameter portion and having a larger diameter than a diameter of the small-diameter portion, the open end is formed in the large-diameter portion, whereby the cylindrical portion, the small-diameter portion and the large-diameter portion are between the diaphragm and the open end, a step with which a peripheral edge of the large-diameter portion is engaged is provided in the joint, the large-diameter portion is bonded to the joint through a bonding portion, the bonding portion is formed between an outer circumferential portion of the large-diameter portion and the joint, where a part of the outer circumferential portion of the large-diameter portion and an inner circumferential portion of the joint are bonded by plastic deformation bonding to keep a connection in the axial direction, characterized by a space configured to prevent a stress caused on the joint when the joint and the large-diameter portion are bonded from being transmitted to the diaphragm is provided between the joint and the first portion.