A method of inexpensive material tester based on the levitation mass method is improved. The tester is composed of an interferometer with Zeeman type two frequency He-Ne laser and a small pendulum as a substitute for a pneumatic linear bearing. As an example of a material tester using the pendulum, which evaluates the mechanical response of general objects against impact forces, is developed. The characteristics of the restoring force are measured under the free-swing condition. To demonstrate the performance of the developed instrument, the viscoelasticity of a gel block under an impact load is evaluated.