With the support of gantry crane operators who load and unload containers between vessels and trailers, we visualized the gap in the line of sight between beginners and experienced operators. The aim was to explore training methods for skills transfer. Through an analysis of eye-movement data, we found that the working environment at 50 m above ground level was psychologically oppressive, so the beginners had an imbalanced gaze to the vital parts of the object. On the other hand, experienced operators made efforts to collect information by widening their gaze range. When it comes to training, in a stressful environment, too much input may instead lead to panic for beginners. Gradually expanding the scope of the inputs becomes important. In addition, beginners also need to carefully imitate the experienced operators in focusing on objects, so that they may truly grasp the skills.