Plagiarism is an act of fraud the work of others people unbeknownst of the author’s original, that violates the Idea Rights and Moral Rights. Actor of plagiarism is done by some academics, especially collage students. Empirically, this study attempted to explore about how the rationality of the background action plagiarism among college students to finished their academic tasks. This research, is qualitative research with a phenomenological approach to Max Weber, that use a knife analysis theory of social action Max Weber and theory of rational choice James S. Coleman. The results of this research showed there are some factor cause students have done plagiarism. Students so interest of this plagiarism, built by instrumental rationality. More students into account about the efficiency, effectiveness and value that is owned by its resources (academic tasks) to achieve their purpose. When the actors (students) determine their purpose, actors will have alternative ways to get it, the alternative way are One Night Finished System and One Work Have Finished. This option will bring a plagiarism action and the consequences of plagiarism action. Keyword: Plagiarism, Rationality, Students.