Spiral springs are widely used in sliding mechanisms because they can store a large amount of elastic energy within a limited space. In mobile products, spiral springs behave in a non-linear fashion. Due to the lack of appropriate analysis methods, spiral springs are currently designed based on experience. Unfortunately, spiral springs can become damaged within a warranty period, indicating that the design strategy needs improvement. Existing analysis methods are limited by excessive simplification or they do not consider the full range of the sliding mechanism. In an effort to identify the causes of spiral spring failure in sliding mechanisms and to establish design guidelines for spiral springs, we developed a finite element procedure for analyzing full sliding mechanisms. The proposed analysis method was verified by comparing the simulated finite element results with those of actual experiments. The simulation results show that the regions of a spiral spring that experience the maximum stress are the same regions in the spring that become damaged during use. The predicted reaction force curves of a spiral spring experienced during operation resemble those measured experimentally. The proposed analysis method is useful for designing spiral springs, with particular consideration for the initial angle of a spiral spring in the sliding mechanism and the cross-sectional thickness and width of the spring itself. The modeling and analysis method used to mimic the spiral spring-based sliding mechanism permits the design of thinner sliding mechanisms with thinner spiral springs. This design may be suitable for use in mobile products.