The optical input device of the present invention comprises a casing, an optical sensor component, a light source and a spectroscopic lens module. The optical sensor component, the light source and the spectroscopic lens module are disposed inside the casing. The spectroscopic lens module comprises a prism, a spectroscope and a lens. The prism is disposed on one side of the light source where light rays are emitted. The spectroscope is disposed on one side of the prism where light rays are emitted. The lens is disposed on one side of the spectroscope where light rays are emitted. The lens module comprising the prism, the lens and the spectroscope allows more images on the medium surface to be captured and enables the optical input device to operate smoothly on glossy surfaces (glass, marble, metal, transparent plastic or photo paper) and multi-colored surfaces.