This paper examines the usage of the Japanese modal adverbs‘Sasuga(ni-wa)’by temporal, genre, and morphological variation in Early Modern Japanese text, and analyze the tendency of stylistic features found in it. Through this survey, the usage tendency of each form of Sasuga(ni-wa)’in early modern materials was found that there are significant differences, focused on the stylistic features that were still inadequate in the historical study of adverbs. In the analysis, while considering the features and precautions of each genre of early modern materials, the Kamigata dialect materials were used throughout the early and late of Edo period, and the Edo dialect materials were used since the Horeki(1751-1764). In addition, the stylistic features of the corpus and manually collected examples of‘Sasuga(ni-wa)’were visually determined. Following this research policy, it was described the overview of the meaning and usage of‘Sasuga(ni-wa)’up to in Pre-Modern Japanese, which is similar to the usage of modern language (Section 2.1). The order of formation and usage of each form of‘Sasuga(ni-wa)’is that the modal adverb usage of‘Sasuga(ni-wa)’began to be seen in Early Middle Japanese text. since in Pre-Modern Japanese, it has been established in the order of‘Sasuga’and ‘Sasugawa, and it is...