An incident angle when illumination light from a position detecting device enters a reflecting surface may be large in some cases. In such cases, the retro-reflection rate of a reflecting surface having a prism structure decreases, leading to a cause of erroneous detection. In order to solve this problem, provided is a reflecting plate including a reflecting surface that retro-reflects illumination light emitted from an optical position detecting device towards the position detecting device that includes a light source, the reflecting plate further including: a surface structure in which a concavo-convex pattern having the same triangle shape in cross-section in a width direction of the reflecting plate continuously appears in a longitudinal direction thereof; and a retro-reflecting layer in which reflecting beads are evenly placed on at least one oblique surface of the concavo-convex pattern.