A torsion tester including a reaction force unit and a drive unit including a servo motor, a first reduction gear, a shaft transmitting an output force from the first reduction gear, a clutch having an input shaft fixed to the shaft, a second reduction gear decelerating rotation of an output shaft of the clutch, a chuck, and a connection mechanism connecting the chuck with one of the shaft and the second reduction gear, the drive unit configured to switch between a first mode where the clutch is disengaged, and the shaft is connected with the chuck by the connection mechanism and a second mode where the clutch is engaged, and the second reduction gear is connected with the chuck by the connection mechanism.