Currently, hydrogen pressure vessels made of carbon fiber reinforced plastic composites (CFRP) for fuel cell vehicles are processed by the filament winding (FW) method: fibers are wrapped around a polymer liner. To reduce the amount of carbon fiber used and to improve productivity compared to the FW method, the development of CFRP pressure vessels with a dome/cylinder bonded structure is expected. For this study, after CFRP pressure vessels simulating a dome/cylinder bonded structure were made, they were subjected to burst tests. A stepped butt-joint structure without using adhesives was applied as the bonding structure. Then the butt-joint length (step length) effects were investigated by experimentation. Internal damage to the pressure vessels was investigated after burst testing using an X-ray CT scanner. In addition, progressive damage analyses based on the finite element method with a cohesive zone model (CZM) were performed to evaluate the experimentally obtained results. The damage behavior estimated by the numerical simulation roughly agreed with the experimentally obtained results. However, all burst pressures predicted by numerical simulation were overestimated compared to the experimentally obtained results, perhaps because of inaccuracies of the parameters used for numerical analyses, such as the critical energy release rate of the delamination.