PURPOSE: To release a diaphragm from being restrained at a support position by the deflection of a leaf spring and to place a proper dynamic load on a test piece by coupling one end of the leaf spring which has lower rigidity when the curved plate of a repetitive fatigue testing device for a ceramic sample with one end of the curved plate and supporting the other end of the leaf spring on the base.

CONSTITUTION: The test piece (p) is mounted on a sample support member 17, an elevation body 20 is lowered to a proper position, and the test piece (p) abuts on a pressure end 22 between said piece and a support end 18, nabling three-point support. At this time, an elastic support material 2 arranged on the reverse surface of the base 1 is compressed and the diaphragm 3 and base 1 are displaced downward to hold the test-piece (p) with constant pressure. In this state, an AC power source 23 applies a voltage to electrostrictive element layers 5a and 5b, the external end of the leaf spring 8 is clamped by washers 12a and 12b with the strain generated in the layers 5a and 5b, so that the diaphragm 3 held on the base 1 enters curved vibration between said diaphragm and a support position. Then the test-piece (p) has both ends pressed downward by the elevation movement of the support end 18 accompanying the curvature vibration and is applied with the curvature vibration as a dynamic load about a pressure point 22.