The purpose of this paper is to clarify the irregular usage of moraic phonemes(/R/, /Q/, /N/) in Japanese internet-based language. In Japanese internet-based language, irregular usage of moraic phonemes has been spreading in this years. In this point, we focus on the usage of irregular moraic phonemes on a youth bulletin site is called Casphy.com. As a result of investigation, we clarified that the irregular usage of moraic phonemes have seven types, and four functions. Eight types of irregular usage of moraic phonemes have a relation on ‘economy principle’, and four functions are characterized by ‘an expression of feelings and personalities’, ‘a substitution of prosody’. In conclusion, it is necessary to clarify the relation between ‘an equivocal usage of marks in the meaning of /R/’ and ‘prosody(intonation)’.