Three-dimensional extrudate swell simulation is a basic calculation technique for the consideration of die shape on a profile extrusion. In this study, we simulated the three-dimensional extrudate swell simulation of polymer melts by the finite element method. The Phan-Thien Tanner model was employed as the constitutive equation for calculation of viscoelastic flow simulation. We carried out the three-dimensional extrudate swell simulation through the straight die having the square cross-section. The extruded fluid swelled at once near the die exit because of elastic recovery. The degree of swelling phenomena near the die exit depends on the elasticity of polymer fluid. The profile of the extruded fluid in the draw region from the profile of the die exit is almost independent of fluid elasticity. However, this profile would depend on the swelling phenomena near the die exit. The comparison between the experimental data and simulation result is needed as the future works.