A method for fast and incremental indexing, with both effective and efficient query processing, is proposed for XML element retrieval. When frequent document updates occur on the Web, they must be handled to maintain the effectiveness of the search system. When new topics are added and document statistics change drastically, search accuracy is also reduced. We therefore consider a method not only for updating indices efficiently but also for processing queries effectively and efficiently. We construct indices for fast updating and propose a method for computing accurate term weights even under dynamically changing statistics. Experimental results show that our proposed system can handle document updates at low cost and search documents accurately even when their statistics change.