This paper presents a 3D virtual eyeglasses try-on system for practical use. For fitting eyeglasses in a shop, consumers wish to look at themselves in a mirror while trying on various eyeglass styles. However, for people who need to wear eyeglasses for correcting problems with eyesight, it is impossible for them to clearly observe their face in the mirror without wearing eyeglasses. This makes fitting them for new eyeglasses difficult. This research proposes a virtual try-on system that can be used while wearing eyeglasses.We replace the user's eyeglasses in the input video with new eyeglasses virtually. Moreover, a fast and accurate face tracking tool enables our system to automatically display 3D virtual glasses following a user's head motion. Experimental results demonstrate that the proposed method can render virtual glasses naturally while the user is wearing real eyeglasses.