Presentation documents have been increasingly used not only as supplementary presentation materials but also as contents for investigative learning. In learning a presentation document, learners generally need to select a number of slides from the document, which describe what they want to learn or should learn. However, it is not so easy to find out the slides to be learnt since what each slide represents is not concisely stated and what connections exist between the adjacent slides are not explicitly expressed. They accordingly take more time for learning and finish learning with incomplete knowledge. In order to address this issue, this paper introduces a map called slidemap for visualizing the logical connections between the slides. This map helps learners identify the sequence of slides to be learnt from the presentation document and grasp the structure embedded in the document in a shorter time. This paper also demonstrates a tool for presentation slides-based investigative learning with slidemap. In addition, this paper reports a case study involving 16 participants with the tool, whose purpose was to ascertain whether using slidemap could be more beneficial for understanding the presentation document than using PowerPoint user interface. The results of the study show the effect of increasing learning time and visiting frequency for slides to be learnt, and promoting learners' understanding of presentation documents in a shorter time. [For the full proceedings, see ED621108.]