This paper describes an ongoing project "Japanese FrameNet (JFN)", a corpus-based lexicon of Japanese in the FrameNet style. This paper focuses on the set of software tools tailored for the JFN annotation process. As the first step in the annotation, annotators select target sentences from the JFN corpus using the JFN kwic search tool, where they can specify cooccurring words and/or the part of speech of collocates. Our search tool is capable of displaying the parsed tree of a target sentence and its neigbouring sentences. The JFN corpus mainly consists of balanced and copyright-free "Japanese Corpus" which is being built as a national project. After the sentence to be annotated is chosen, the annotator labels syntactic and semantic tags to the appropriate phrases in the sentence. This work is performed on an annotation platform called JFNDesktop, in which the functions of labeling assist and consistency checking of annotations are available. Preliminary evaluation of our platform shows such functions accelerate the annotation process.