A simplified analytical method is applied to vibration analysis of a commuter railway vehicle. Vibrationmeasurement test results for a real commuter vehicle show that the vibration characteristic of the vehicle is verycomplex; therefore, usual beam model cannot be applied. In the proposed method, the carbody is modeled as abox-type structure; this enables to express three-dimensional elastic vibration of carbody. A numerical model forthe commuter vehicle is established by using the method. Numerical results are compared with the experimentalresults. Good agreement is observed for natural vibration mode properties and frequency response functions.Some vibration suppression measures are examined by using the numerical model, and it is found that to increasebending rigidity of the floor is more effective than increasing vertical bending rigidity of the side lengthwisemember.