Visualization systems for hierarchical structures, especially for huge data structures, have a potential usefulness. However, it is meaningless to visualize such huge data with a current tree visualization framework. With an exponential explosion in size of a tree, when users focus on a node, they cannot see the minimum information, such as its parent, children, or siblings, in a scrollable window. Also, the increase of visual elements is detrimental to the human's cognitive load as well as to the system's response time. we proposed fractal approaches to these problems. The geometrical characteristic of a fractal, self-similarity, allows users to visually interact with a huge tree in the same manner at every level of the tree. The fractal dimension, a measure of complexity, makes it possible to control the total amount of displayed nodes. A prototype visualization system for UNIX directories is also shown.