During tube bending, the tube has appeared to be wrinkling and thickening on the inside of the bend, as well as flattening and thinning on the outside of the bend. In addition, there is the spring-back that is caused by elastic deformation after unloading. Thus, the stiffness of a bent tube can be changed according to the deformation characteristics. Because the Inconel 625 fine tube is used in an extreme environment of high pressure and high temperature, the stiffness change of the bent tube has an important meaning. The aims of this study are to predict the deformation characteristics and stiffness change of a fine tube with an outer diameter of 1.5 mm and a thickness of 0.12 mm in the bending process. For the elasto-plastic FE analysis, a tensile test was performed to obtain the true stress-strain curve of the solution-treated fine tube. The elasto-plastic bending FE analysis was performed to observe the deformation characteristics such as flattening, wall thinning and wall thickening of the bent tube at room temperature. A structural analysis was also to predict the exact stress level of the bent tube with a deformed cross-sectional shape under a pressure of 10 MPa. The maximum tensile stress was observed on the inner surface of the connecting part between the flattened part and the circular part. The result of the FE analysis, revealed that the changes in the cross-sectional shape of the bent tube was the main cause of increased stress and most significant characteristic in view of the stress level.