Recently, seismic diagnosis and reinforcement design for railway embankments have been conducted in Japan. In the seismic diagnosis for the existing embankments, it is general to adopt the saturated strength characteristics of embankment materials evaluated from triaxial compression tests using specimens sampled at representative points. This evaluation method for their strength characteristics corresponds to the assumption that the density of the embankment is uniform and that the entire area is saturated. The seismic resistance of the embankment may be underestimated compared to its actual resistance, and the quantity of reinforcement required to ensure seismic stability and the construction costs increase. This paper examined the estimation method for the density distribution of embankment from shear wave velocities. In this method, the density is estimated from the shear wave velocity obtained by surface wave exploration, referring to the results of bender element tests with different densities of specimens. The estimated results were generally consistent with the densities measured in the field, suggesting that it may be possible to estimate the density distribution of the existing embankment. The seismic diagnosis for railway embankments was conducted considering their dry density distribution evaluated by the proposed method, and the results were compared with those of the conventional method to confirm the increase in the factor of safety during an earthquake.