The aim of this paper is to consider about "logic" in teaching expository text. In studies to teach reading expository text, developments of instructional theories brought extension of using the word "logic", and it has a lot of meanings. At least there are four approaches to "Logic", logistic, rhetorical, linguistic, and epistemological. In recent years, Toulmin's model of argument is often used to teach expository text, but the relations among argument, coherence and retoric are not considered enough. In this paper, I analyze them in an expository text entried on Japanese textbook of junior high school.