This study investigated the appropriacy of North Korean vocabulary in the 15 different kinds of Korean textbooks developed in line with the revised Korean Language Curriculum in 2007. For this, I strongly suggested three criteria such that the North Korean vocabulary in textbooks are useful for learners to achieve their objectives (purposefulness), they contribute to Korean preparing the Korean Language for the unified Korea(usefulness) and they are frequently used in the spoken and written language of North Korean(frequency). The result of researches on the North Korean vocabulary of textbooks based on these three criteria, the following problems were discovered. First of all, the textbooks do not correctly present the relationship between South Korean vocabulary and the North Korean vocabulary, which it leads learners to misunderstand the vocabulary differences between the South Korean vocabulary and the North Korean vocabulary. Secondly, there are only a few homographs used in the textbooks even though they are useful for the preparation the Korean Language that can probably be used in case of the unification of two Koreas. Third, there are some words that are not currently registered in the dictionary and not even used any more in North Korea. From now on, when we cover the contents on the vocabulary differences of South Korean and North Korean, it is necessary for the textbooks to contain those North Korean vocabulary which are appropriate to these three criteria.