PURPOSE: To perform automatically the bending test under stable conditions by bending an object to be tested, which is fixed to round frames, repeatedly along outside circumferences of two round frames alternately in accordance with the motion of two turntables which are reversed after being rotated at a prescribed angle.

CONSTITUTION: An object A to be tested is arranged obilquely between round frames 15 and 15' and has both ends fixed to individual round frames or turntables rotating them by wires 16 or the like, and limit switches 13 and 13' are adjusted to set positions after projections 14 and 14' of turntables reach a desired rotation angle θ. Turntables are driven to rotate two round frames 15 and 15' in the reverse direction, and the object A to be tested is bent along the outside circumference of one round frame 15. The limit switch 13 is operated, and turntables are reversed together by this signal, and the object A is bent along the outside circumference of the other round frame 15' to form a reverse bend. This operation is repeated to perform automatically the bending test of the long- sized material.