An optical device includes a clamp seat and a light tuning assembly. The clamp seat includes a base, a curved portion extending from the base, and a pressing portion extending from the curved portion. The light tuning assembly includes a support frame disposed at the base, an optical lens restrained by the support frame, and an adjusting member coordinating with the optical lens. In an application of the optical device, a user may clamp a multimedia mobile communication device by the base and the pressing portion to allow the optical lens to align with a light projecting assembly of the multimedia mobile communication device. The adjusting member is rotated to adjust a distance between the optical lens and the light projecting assembly. Light from the light projecting assembly is then focused or dispersed through the optical lens to solve an issue of unadjustable light of a conventional solution.