The purpose of this study is to compare and discuss how well the publisher, ChatGPT, and NMT have preserved 'naturalness' in translating TOEIC textbooks. In order to engage in such a discussion, we compared and analyzed all the translations in the beginner-level TOEIC textbook's explanation booklet provided by Company H. These were classified into four categories for analysis: firstly, 'violation of naturalness' due to excessive use of foreign language, secondly, 'violation of naturalness' due to indiscriminate use of passive/active voice, thirdly, 'violation of naturalness' due to abbreviated translation, and fourthly, 'violation of naturalness' due to literal translation of vocabulary. The analysis results revealed that none of the three types of translations perfectly preserved 'naturalness.' In particular, Company H's textbook translations required a slightly more learner-oriented naturalness than ChatGPT or machine translations.