Axially loaded rubber blocks of circular cross-section whose ends are bonded to rigid plates are studied. Frequency-response functions were obtained with finite-element model on rubber specimens, with respect to Poisson's ratio and shape factor. Than apparent Young's modulus was estimated and various equations that describe relationship between the apparent Young's modulus and actual Young's modulus of rubber material were used to estimate Young's modulus of rubber material. Further estimated Young's modulus of rubber material was compared to one defined in finite-element model.It is shown that there is a significant difference in estimated Young's modulus when different equations were used, especially when Poisson's ratio of rubber material is smaller than theoretical 0.5.