This paper proposes the real-time stereoscopic conversion method with adaptable viewing distance by the viewer's eye detection at personal stereoscopic viewing devices. The distance between a screen and viewer is often changed by moving a personal display or moving head position. It causes a visual discomfort and low quality stereoscopy. Our proposed method is divided into two parts; eye detection part to acquire viewer's eye positions and stereoscopic generation part in real-time. In the first part, we can measure an interocular distance of a single viewer by the proposed eye detection method and also calculate the distance between a screen and a viewer by using the principle of stereoscopic generation. In the other part, we propose an efficient motion-based approach for conversion from 2D video to stereoscopic video. The disparity between left image and right image is adaptively adjusted by viewer's interocular distance. Adaptation time for a 3D immersion during 3D stereoscopic viewing is remarkably reduced and stereoscopy is personally optimized. Therefore, our proposed system can offer optimized stereoscopic conversion and more freedom of viewer's head considering the distance between a screen and a viewer through the proposed eye detection.