Boilers and pressure vessels are heavily used in chemical industrial plant. The equipments are investigated the presence of damages periodically. The most damage types in the equipments are a wall thinning. Any damage must be repaired or replaced as necessary. On the other hand, optimization of the time required in order to replace damaged equipment by evaluating the load carrying capacity of pipes with wall-thinning is expected in chemical industrial field. In the present study, the estimated burst pressure of pipes with rectangular-wall-thinning is calculated by using FEA. And then, the estimated burst pressure is compared with experimentally obtained burst pressures. The estimated burst pressures agree well with the experimental results, because the difference between the estimated burst pressures and the experimental results is within ±10%.