In this study, we revealed the enhancing mechanism of the tactile sensation through a flexible coil spring. Flexible coil is a new device that amplifies tactile sensation on small undulating surface, and is a small structure of 1.2mm thickness and 2.6mm width. A two-dimensional kinetic model of the spiral coil was developped to analyze the behavior of the "pin-part" of the flexible coil when the coil is tracing undulation surfaces. The results of the simulation analysis indicated that the coil causes lateral strain on the skin surface of ball of a finger.