A car structure is provided which has the required strength against vertical load and vibration while avoiding increase in weight of the structure. At an entrance 6 of the railroad car structure 20 in which a side structure 2 is formed by a hollow member, the side structure 2 and a frame 7 are coupled via an L-shaped fitting 10. The L-shaped fitting 10 consists of a first joint part 10a which is in the form of a plate and couples a vehicle outer face plate 8 and a vehicle inner face plate 9 and a second joint part 10b which is in the form of a plate and butt welds a part of the first joint part 10a near the vehicle outer face plate 8 and the frame 7. Plate thickness of the second joint plate 10b is larger than plate thickness of the vehicle outer face plate 8. As a result, the required strength against vertical load can be ensured without increasing the plate thickness of the vehicle outer face plate 8, in other words, with little increase in weight of the structure.