In sensors, integrated reflection mechanisms of the illuminating light to the reflection material on the proof mass require a strict single degree of motion because the accuracy almost entirely depends on the motion of the proof mass. Therefore, this paper describes the optimum design of a mass-spring structure that features high sensitivity and long linear elastic motion range of the leaf spring without rotation and lateral motion of the proof mass. Accordingly, finite element analyses were conducted to determine an optimal leaf spring pattern and to predict the probe performance. The optimum design of the leaf spring was determined by considering five criteria within the linear elastic region of the eight leaf spring models. Then, two types of leaf springs were manufactured, and the proposed mass-spring system integrated to the prototype was fabricated. The reliability of the FEA results and the performance of the fabricated mass-spring model were verified through the force-displacement curve test, the dynamic test, and the rotation test.