PURPOSE: To determine the bead characteristics accurately by detecting a compressive force being applied to each angular position along the inner circumference of tire bead when a plurality of fixing means abutting on the inner bead of tire moves radially outward.

CONSTITUTION: A tire 2 is set on a fixing means 4 with the tire bead directing upward. When a ram member 18 is moved downward by an operating mechanism, a measuring part body 3 is also moved radially outward and a stretching force is applied to each part 26 of the inner bead of tire touching each fixing means 4. The force is transmitted between the ram 18 and the inner bead through the vertical part 8 and upper/lower outer parts 6, 7 of a frame mechanism being guided by a guide mechanism 20. The force applied to the mechanism is transmitted through supporting parts 9-12 to a transmitting part 5. Strain gauges 13-16 detect the deformation of supporting parts 9, 10 caused by application of stretching action to the inner bead. Detection signals are fed through an amplifier 22 to a signal processing circuit 23 where the signals are processed and the compressive force at each position on the circumference of tire is presented on a display 24.