This study identifies the meaning and variety of the functions of “nanimo” regarding its negative expression in modern Japanese language. In past research, various aspects and characteristics of “nanimo” as negative expressions have not been thoroughly investigated. This study surveys examples from several resources such as BCCWJ and is able to identify the distinctions of “nanimo” in response to negative expressions, including its meaning and functions. First, the findings identify two distinct meanings of “nanimo” in negative expressions; an inward and an outward meaning, with their own distinct characteristics that are not compatible each other. Second, the meanings and functions of “nanimo” are sorted into several categories such as a quantitative, adverbial, dual, exclamatory, and emphasis application. Finally, negative expressions not responding to “nanimo” are also discussed. This research identifies expressions without reasons such as “～wake ga nai,～hazu ga nai,” expressions, which described phenomena or discovery like “～ga nai,” and where “nanimo” is not used with negative adjectives. Furthermore, in case of positive expressions, “nanimo” is not used together. Additionally, when evaluations of audience is included in one’s expression, “nanimo” is not used.