This paper describes about a new testing machine devised for fatigue test under repeated impact at high frequency and the test results obtained by it.The mechanism of machine is as follows:When a crank mechanism makes the upper end of the spring reciprocate, an impact hammer, which is hung from the lower end of a spring, receives a forced oscillation in vertical direction, so that the hammer may impact a test roller-chain through a cross-piece.The result on the theoretical consideration of the oscillation of the hammer and that obtained by experiments are as follows:(1) When the crank radius and the clearance between the impact hammer and the cross-piece are suitably set, the machine operates steadily in a satisfactory condition.(2) By raising the resonance point of the machine, we can make tests under higher frequency.(3) Using the resonance by the spring, the machine does not bring unnecessary impact and consumes just a little power.(4) The fatigue test result about test roller-chain was satisfactory with little dispersion.