This study focuses on the design and development of a changeable mold for various pattern molding applications. The proposed mold is lightweight compared to conventional molds, enabling operators to easily replace the pattern surfaces. Structural analysis was employed to optimize the mold design. Initially, the clamping force was distributed across the contact area to ensure that the stress remained below the yield strength. Subsequently, the thickness of the cavity surface and the number of bolts securing the cavity surface to the mold base were optimized. Based on the structural analysis results, the deformation and stress were evaluated, and a thinner and lighter cavity structure was achieved compared to the existing mold. The mold's weight was reduced from an initial 56 kg to 18.4 kg, achieving a weight reduction of approximately 68%. The lightweight mold developed in this study is expected to significantly enhance work efficiency by allowing operators to replace molds more easily.