The main purpose of this study is to diagnose validity and effectiveness of directive sentence in Korean textbook for foreign learner using the corpus-based approach. It evaluates directive sentences according to textbook's level by three criteria such as structural complexity, variations of grammatical forms and words, and validity of using grammatical forms and words fit to the certain level. In structural complexity diagnosis, frequencies in use of words, clauses per directive sentence which are shown in every sentence are measured in an assumption that the level of textbook became higher; the complexity of directive sentence is higher. In variations in words and expressions diagnosis, the cumulative frequencies in use of various forms are evaluated in directive sentence. In validity of using words and expressions of communication diagnosis, it will be investigated whether the directive sentence are constructed with words and expressions which are studied and understandable, by comparing with the list of words and expressions of the textbooks. It may be expected that the result of this study can be utilized in developing textbook and language proficiency test such as TOPIK. (Yonsei University)