Not a few scientists did write their scientific papers inr omaji (or Roman script) or advocated to write Japanese in romaji in the period between 1880s and 1940s. Other people than scientists, such as Japanese linguists, educators, politicians and businessmen, were indeed among proponents of writing in romaji. And those people working in different sectors in society united to carry out campaigns to promulgate among the public the use of romaji in writing Japanese sentences. The campaigns have been designated Romanization Movement. Why, then, did scientists get involved in the movement? Did they have any interest specific to scientists in writing in romaji? Did they present any distinctive causes as scientists in the movement? The paper aims to answer these questions in taking into account the following circumstances that Japanese scientists had to meet after Meiji Restoration in 1868. Scientists generally communicate their achievements not only to the members of scientific community but also to the general public in cooperation with educators, science journalists, and others. However, when Japanese scholars started scientific research in 1870s, all members of scientific communities around the world, except those of fledgling societies in Japan, did not understand Japanese, while the general public who were to absorb scientific ideas only knew Japanese language and could use kanji (or Chinese character), and kana (or phonetic syllabic script consisting of two separate forms of katakana and hiragana), though they were troubled with kanji's complexity and inconvenience. The analysis that follows explicates what happened with regard to language, terms, and script used in scientific communications between scientists, and scientists and the public in a country where native language was not English or other Western language commonly used in scientific world. The paper also discusses what the history of the Romanization Movement implies for science communication in these days in Japan.