Recently, permanent magnet motors are widely used in many industrial fields because they are suitable for compact mechanical system. The motor core is usually manufactured from magnetic steel sheet with press machine. However, usually most parts of the plate are scraped, and only small percent of the sheet is used for the core. The spiral accumulating core system is suitable for manufacturing the core more ecologically because in this system more than 50% of the magnet steel sheet can be used. In this study, therefore, the effective Young’s modulus of the spiral accumulating core is considered in order to find out a good method to fix the core. In this analysis, the finite element method is applied to 3D models, whose layers and slits are periodically arranged. Stress and thickness distributions are also analyzed in the bending process. When the spiral core is manufactured through spiral accumulating system with plate-bending process, the thickness change should be minimized because that may deteriorate dimensional accuracy of the spiral core. Also residual bending stress is investigated because that may cause an electric loss. The results indicate that plastic zone is limited at localized regions and therefore an electric loss is not very large. The effective Young’s modulus of the 3D dimensions model of the real spiral accumulating core is estimated about 127.5 GPa.