The aim of this study is to investigate the geometric effect on the inhomogeneous deformation behavior along the thickness direction as well as the radial direction of the workpiece during high-pressure torsion (HPT) using the finite element method. The simulation results show that the area of the dead metal zone at the corner in the edge of the workpiece decreased with increasing the angle of the lateral wall of the depression in the HPT die, resulting in relatively homogeneous deformation during HPT. Furthermore, the friction force on the lateral surface of the workpiece affecting the deformation inhomogeneity increased with increasing the depth-to-radius ratio of depression. Therefore, it was concluded that the strain inhomogeneity along the thickness direction can be minimized by controlling the die geometries.