This study analyzed English words that are used in the middle school English text books of the 6th and the 7th National Curriculum in Korea. For this analysis, an English corpus of a total of 1,230,023 nodes was built out of 63 English textbooks of the 6th and the 7th National Curriculum. The study specifically investigated the following items for analysis: 1) tokens and types of words used in the middle school textbooks, 2) frequency of the words, and the numbers of new words introduced in each school-year, 3) high-frequency words in the textbooks with reference to those in large-scale general English corpora, 4) parts of speech of the words and their frequencies, and 5) the comparison of the words used in reading parts and listening parts. Analysis of the corpus revealed the following results. Regarding the average number of tokens and types, the textbooks based on the 7th Curriculum contain more than those based on the 6th Curriculum. As for the frequency of the repetition of words, the 6th curriculum textbooks are more than the 7th curriculum textbooks. Comparison of vocabularies used in the text corpus and in general large-scale English corpus shows that there are more similarities than differences.