An axial force measurement device including: a frame; a tightening actuation unit that performs tightening operation upon a screw type tube fitting installed upon a tube upon which is formed an annular portion projecting in the radially outward direction from the tube; a testing member; and a mating member holding unit that holds the testing member into which the tube fitting is screwed and that is coupled to the tube, with the tightening actuation unit and the mating member holding unit being provided to the frame in line along the direction of a reference axis that extends in the direction of the center line of the tube fitting and the tube axis of the tube, wherein the axial force measurement device is characterized in that the testing member has: a first part (TMa) through which is pierced a screw hole in which an internal thread that engages with the tube fitting is formed; and a second part (TMb) having a bottom portion against which the annular portion of the tube is pressed; and the mating member holding unit holds the first part (TMa) and the second part (TMb) in a state in which the screw hole of the first part (TMa) and the bottom portion of the second part (TMb) are concentrically abutted against one another, and wherein one of the first part (TMa) and the second part (TMb) is held by the mating member holding unit in a state in which it cannot shift along the direction of the reference axis, while movement of the other of the first part (TMa) and the second part (TMb) is restricted in the direction of the reference axis in a state in which a load cell that outputs a signal corresponding to the load in the reference axis direction is interposed. a frame; a tightening actuation unit that performs tightening operation upon a screw type tube fitting installed upon a tube upon which is formed an annular portion projecting in the radially outward direction from the tube; a testing member; and a mating member holding unit that holds the testing member into which the tube fitting is screwed and that is coupled to the tube, with the tightening actuation unit and the mating member holding unit being provided to the frame in line along the direction of a reference axis that extends in the direction of the center line of the tube fitting and the tube axis of the tube, wherein the axial force measurement device is characterized in that the testing member has: a first part (TMa) through which is pierced a screw hole in which an internal thread that engages with the tube fitting is formed; and a second part (TMb) having a bottom portion against which the annular portion of the tube is pressed; and the mating member holding unit holds the first part (TMa) and the second part (TMb) in a state in which the screw hole of the first part (TMa) and the bottom portion of the second part (TMb) are concentrically abutted against one another, and wherein one of the first part (TMa) and the second part (TMb) is held by the mating member holding unit in a state in which it cannot shift along the direction of the reference axis, while movement of the other of the first part (TMa) and the second part (TMb) is restricted in the direction of the reference axis in a state in which a load cell that outputs a signal corresponding to the load in the reference axis direction is interposed. a first part (TMa) through which is pierced a screw hole in which an internal thread that engages with the tube fitting is formed; and a second part (TMb) having a bottom portion against which the annular portion of the tube is pressed; and the mating member holding unit holds the first part (TMa) and the second part (TMb) in a state in which the screw hole of the first part (TMa) and the bottom portion of the second part (TMb) are concentrically abutted against one another, and wherein one of the first part (TMa) and the second part (TMb) is held by the mating member holding unit in a state in which it cannot shift along the direction of the reference axis, while movement of the other of the first part (TMa) and the second part (TMb) is restricted in the direction of the reference axis in a state in which a load cell that outputs a signal corresponding to the load in the reference axis direction is interposed.