Fractal geometry Most of the configurations of natural phenomena such as crystal of snow, outline of clouds, structure of trees have common patterns between the whole structures and the substructures. This theory built on the system of self-similarity is developed by Benoit Mandelbrot and is called to be fractal theory. In the field of Computer Grafics, this theory is often be used for simulating the natural phenomena. Spectral concept Analysing those fluctuating physical phenomena by use of power spectral concept, spectral functions of some of these phenomena are reciprocal of the frequency. This finding is also obsearved in human physical conditions such as brain wave, heartbeat and so on. Professor Musha implies that the fluctuations which follow this finding make us find them natural and affective. Scope This paper discusses the visual response to various vertical stripe patterns: a) fractal stripes b) stripes of which specra are reciprocal of frequency c) an equi-spaced stripes d) random stripe patterns ) Traditional patterns in Japanese architectural works Conclusions (1) the general flow of the computer program to generate stripe patterns were presented which follow the fractal concept and power spectral one. (2) fractal stripe patterns make us find them natural, and naturality is a linear relation to the similarity dimension. (3) the stripe patterns which follow the spectral concept make us find them natural and affective.