For the recent railway vehicles, reduction of three-dimensional elastic vibration of the carbody is required for improving the ride comfort of passengers. In order to study the vibration reduction technique efficiently, an analytical model which can deal the three-dimensional elastic vibration is needed. This paper proposes a new analytical model, in which the roof, floor, sides and end panels are modelled as anisotropic three-dimensional elastic bodies treated as continuous system. These components are connected with each other by artificial translational springs between them. This model has smaller degrees of freedom (about 3,500) than those of the detailed finite element (FE) model (more than 500,000), and it has advantages in model creation time and computational cost. Furthermore, a method for determining its parameter values efficiently using an optimisation technique is proposed. As the modal analysis results, good agreements are obtained between the measurement results and calculation ones with respect to the mode shapes, and the error of the natural frequencies is within 1.7%. From these results, the proposed model can deal various three-dimensional elastic vibrations, and the valid parameters can be determined by the parameter updating method.