In power plants, bending deformation of turbine rotors can occur due to severe operating conditions such as highspeed rotation, high temperature and pressure. Therefore, it is necessary to straighten the bent rotors fast and effectively. This study focuses on a numerical simulation of the opposed heating and cooling method, which is one of simple straightening ways. First, an appropriate magnitude of heat flux, which is used as input data of numerical simulations, is estimated by comparing the simulation results with experimental ones of a flame heating. Next, we conduct finite element analysis of thermal deformation during the heating and cooling processes, and also predict the residual stress after straightening the bent rotors.