Achieving quiet and comfortable ride in a railway passenger car requires elastic vibration analysis of the passenger car body as a three-dimensional structure. This paper presents experimental and theoretical analyses of elastic vibration of a passenger car body at less than 30Hz. The body structure has one floor, two sides, one roof, and two ends, and each of these is composed of stringers, cross members, columns, reinforcements or panels. The three-dimensional FEM model has 670 elements, which are all beam or panel elements. The cross section of the model is formed from 11 connected straight lines, including 3 lines in the side and 4 lines in the roof. The theoretical analysis shows good agreement with the experiment, especially in the one-node floor bending, and slight difference in the two-node and the three-node floor bending.