This paper proposes a new tool called Cubic Gantt Chart,3D version of Gantt Chart for visualizing e-learning activity data such as how long and how often students look at each page of an e-learning material like PowerPoint slides.Using a dedicated tool called BookLooper can collect these activity data.The analysis of e-learning activity data is significant for instructors to understand students learning states and the difficulty levels of e-learning materials because those can suggest more efficient instructional ways.So,in this paper,the authors propose Cubic Gantt Chart as a visualization tool for the analysis of students e-learning activity data and justify its usefulness by showing visualization examples of actual data collected by BookLooper.