Recently, permanent magnet motors are widely used in wide 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 scalped, 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, effective Young’s modulus of spiral accumulating core used for permanent magnet motor is considered by the application of the finite element method to 3D models, whose layers and slits are periodically arranged. Then, effects of slits, layers and embossing interlockings on effective Young’s modulus are analyzed. Finally, a convenient method of calculation based on rule of mixture is newly proposed for estimating the effective Young’s modulus of the real spiral accumulating core.