This paper describes a novel navigation planning method that generates a plan (a sequence of Web pages) guiding concept understanding in the WWW (World Wide Web). It also has the ability to generate operators during planning from Web pages using keyword extraction methods. When a user wants to understand a concept, it is useful to browse for relevant Web pages in the WWW. However, in general, this task is very hard because the user does not know where such Web pages are, and has to search for them in the vast WWW search space. Even with a search engine, this consumes the user’s energy. To deal with this problem, we propose navigation planning to automatically generate a sequence of Web pages by which a user systematically understand a target concept. First, with a planning framework, we formalize the browsing task in the WWW. Action is defined as the understanding of a Web page, and an operator for a Web page consists of conditional/effect knowledge. Unfortunately it is impossible to prepare operators for all the Web pages. Hence we develop a method to generate an operator from a Web page by extracting condition/effect terms with keyword extraction techniques. Then the whole planning procedure is describes. Finally we fully implement the navigation planning system and make experiments by comparing with methods using a search engine and link-tracing (like a Web robot). As results, we found out navigation planning is a promising approach to assist the concept understanding in the WWW.