Radiation impedance of a circular vibrating plate on the surface of sand varies with the viscoelastic properties of sand. Therefore, it is possible to predict the viscoelastic properties using the characteristics of the radiation impedance. In this study, the characteristics of the radiation impedance of a circular vibrating plate on the surface of viscoelastic media were obtained by numerical analysis. The results show that the frequency at which the imaginary part of the radiation impedance becomes zero, is proportional to the shear wave velocity of viscoelastic media. The density of the media can be obtained using the values of the real part of the radiation impedance and the predicted shear wave velocity. Next, the radiation impedance for dry and water saturated beach sand were measured, and the measured values were compared with the calculated values using the equivalent Lame's constant of sand.