The purpose of this chapter is to discuss the semiotic approach to form theory of computer visualization. Such theory should be the foundation of design, development, and evaluations of visualization systems. The “direct” semiotic analysis of visualization is defined and the scheme of the analysis is considered. This analysis reveals “who is who” in the process of the visualization semiosis and helps in design and development of the real visualization systems. The analysis allows to describe the problems arising at developments of specialized systems in terms of the semiotics and showing how this analysis can serve as a tool for the visualization systems design. It is important to analyze the sign nature of the human‐computer interface and the visualization. Such conceptions as computer metaphor, metaphor action, and metaphor formula are defined. The properties of metaphors are analyzed with a view to possible usage of metaphors for specific applications. The properties are considered by the example of the hierarchical sequence of the natural Room‐Building‐City (Landscape) metaphors. Also the properties of the molecule metaphor are considered in the context of software visualization systems. In conclusion, some approaches to the theory of computer visualization are outlined.