In this paper, the reasons of die fracture occurring in hot aluminum forging of a fixed scroll are investigated using finite element analysis. A forging process tried out to develop an aluminum scroll for medium-sized electric vehicle is simulated using a rigid-thermoviscoplastic finite element method and the predictions of stresses along the die=material interface are employed for die structural analysis. The effective stress of die and y-directional stress component is examined to reveal the reason of die fracture, revealing that excessive bending stress due to flow unbalance induced lateral force exerted on the warp, i.e., protruded die part leads to the die fracture.