Bogie is the connection device between carbody and wheel in railway vehicles. It is the core part that exert a important effect on the passenger safety and running safety. Bogie largely consists of the bogie frame, suspension, air brake system and wheel set. A static and dynamic load have acted on it complexly. When the bogie is designed, a finite element method, static load test, fatigue test, running test should be considered. A welded structure type bogie was developed for high speed freight car. But some bogie frames have the problems in end beam. There were some cracks ine end beams. The crack situation of the end beam have a bad effect on the brake system. In that case, the cars would be in danger of derailment. This report shows the cause of end beam crack, improvement method. In order to clear the crack cause, many tests were tried. The test result concludes that the crack cause of the end beam is not the brake load but the vibration at the real line running on the track. It is estimated that the improved car which end beam was reinforced was safe enough within permitted life of the car (25years). On the basis of the results, the existing end beam was improved. The safe of the improved end beam was proved by real line test on the track. The operation of freight car have no problems any more.