In a search server, a page collection unit collects Internet pages. An index generation unit generates an index of the pages. An index-tree generation unit generates an index tree representing the connection relationship among the pages in a tree structure, and in which a page linked from multiple pages is represented by different nodes in a duplicated manner. When a search word input unit inputs a search word in a client, a search-result generation unit of the search server generates a search result on the basis of the index. For the index tree, a search-result-tree generation unit, for example, highlights nodes containing the search word, and deletes nodes, each of which does not contain the search word and is not a branch point into multiple branches which contain the search word. The search-result-tree generation unit outputs the resulting search result to a search result display unit of the client.