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 10 a 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 10 b which is in the form of a plate and butt welds a part of the first jointpart 10 a near the vehicle outer face plate 8 and the frame 7 . Plate thickness of the second joint plate 10 b 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.