One year after the construction completion, the occurrence of fracture of high strength bolts was found in Ayeyarwady Bridge （Yadanarbon）, Myanmar. As high strength bolts are used for the connections, fracture due to the hydrogen embrittlement is inevitable. However, the fracture happened very early and many bolts were broken from June 2010 until 2015. Defect in the raw material or fabrication defect that can accelerate the early fracture of the bolts is suspected. In this study, visual observation, sectional tissue and hardness testing were conducted to investigate the fabrication defect of the high strength bolts.