A lens structure including a quarter wave plate layer and a linear polarizing plate layer is provided. When the linear polarizing plate layer is located at an outer side of the lens away from a viewer's eye, the polarizing axis of the linear polarizing plate layer is in a vertical direction. The lens structure can be used to make dual-purpose eyeglasses with sunglasses and 3D glasses functions. Any one of the quarter wave plate layer and the linear polarizing plate layer can be disposed at the outer side away from the user's eyes by adjusting the orientation of the lens of the present invention. When the linear polarizing plate layer is located at the outer side away from the user's eyes, the optical axis of the linear polarizing plate layer is in the vertical direction. Thus, the dual-purpose eyeglasses with both sunglasses and 3D glasses functions can be achieved.