Torsion tester

Provided is a torsion tester that is provided with a drive unit, which rotatably holds one end of a test specimen, and a reaction force unit, which is affixed to the other end of the test specimen, and that imparts a torsion load to the test specimen by means of rotating the one end of the test specimen by means of the drive unit. The drive unit is provided with: a servo motor; a first reduction gear that reduces the rotation of the servo motor by a first reduction ratio; a shaft that transmits the output of the first reduction gear; a clutch to the input shaft of which the shaft is affixed; a second reduction gear that reduces the rotation of the output shaft of the clutch by a second reduction ratio; a chuck that is rotatably supported; and a coupling means that switchably couples the shaft or the output shaft of the second reduction gear to the chuck. When the input shaft and the output shaft of the clutch are separated and the shaft is coupled to the clutch by means of the coupling means, operation is performed in a first mode, and when the input shaft and the output shaft of the clutch are coupled and the output shaft of the second reduction gear is coupled to the chuck by means of the coupling means, operation is performed in a second mode.