A testing method for precision force measurement using a small pendulum based on the levitation mass method (LMM) has been developed. In this method, the force acting on the material to be tested is measured using an optical interferometer. In this paper, a collision test of the spring and the pendulum is performed. As the result of the test, the maximum force on the spring was evaluated as approximately 0.533 N. To demonstrate the performance of the developed instrument, the impact responses of the pendulum are accurately evaluated. The possible applications of the developed method are also discussed.