PURPOSE: To provide a central position measuring device and concentricity control device which can measure a change of the central position of an upper mold assembly in a stroke extending from a holding position where a green tire is held by top and bottom forces up to a clamping position where the top and bottom forces are clamped and perform positional control of the upper mold assembly.

CONSTITUTION: A central position measuring device is constituted of square piller members 2, 3 possessing a height H which is at least a stroke S of an upper mold assembly 34 extending from a holding position 1) of a green tire which is provided in a suspending state to the upper mold assembly 34 by a top and bottom forces to a clamping position 2) of the top and bottom forces and two perpendicular planes meeting at an appropriate angle and a noncontacting distance sensors 5-8 corresponding to the respective perpendicular planes each of the square pillar members 2, 3. Then a concentricity control device is constituted of a cylinder arranged to a side part of the upper mold assembly 34 and a control device 15 giving operation command to the cylinder based on a measured value of a central position measuring device.