The Impact Vibration Test is now regarded as a major method to evaluate the conditions of bridge substructures. However, because of its low rigidity, the conditions of circular section piers cannot be evaluated by this test. In other words, because bending vibration is superior in these piers, it is difficult to evaluate the conditions of the bearing capacity of the foundation. First, this paper proposes how to estimate the standard values of the natural frequency of the circular section piers. Secondly, the Vertical Impact Vibration Test was tried to measure the vertical natural frequency. As a result, the validity of both evaluation techniques was verified.