Based on the discourse functional approach, this paper examined from the driving force of the backchannel of ‘geureonikka(그러니까)’ to the appearance of the discourse of it. The summary of this paper is as follows. First, the driving force of the backchannel of ‘geureonikka(그러니까)’ is the conjunctive ending ‘-nikka(-니까)’ that constitutes ‘geureonikka(그러니까)’. The ‘-nikka(-니까)’ puts the preceding clause in a premise position, which makes ‘geureonikka(그러니까)’ what the conversation participants already know about the information of the interlocutor’s utterance. In addition, due to the characteristic of ‘-nikka(-니까)’ giving a justification to the following clause, ‘geureonikka(그러니까)’ gives a justification to the preceding utterances interlocutor was speaking just before. This shows that the conjunctive ending ‘-nikka(-니까)’ is the driving force of the backchannel of ‘geureonikka(그러니까)’. Second, in the process of discourse markers, ‘geureonikka(그러니까)’ was dedicated to the meaning of the entire phrase ‘geureonikka(그러니까)’ that expresses consent and sympathy with the interlocutor’s utterances. The following utterances of the entire phrase ‘geureonikka(그러니까)’ to agree with the other person’s utterance is usually something that the speaker and listener can guess. As a result, following utterances were frequently omitted, and ultimately, only ‘geureonikka(그러니까)’ was enough to express consent and sympathy for the interlocutor’s utterances. This made ‘geureonikka(그러니까)’ to be used as a marker of backchannel in the discourse dimension. Third, ‘geureonikka(그러니까)’ was appearing in the discourse due to the interactive requirements of ‘-jan-(-잖-)’ and the rhetorical question. The ‘-jan-(-잖-)’ and the rhetorical question have assumed that the content and the answer of the utterance are already shared by the speaker and the listener. In other words, the speaker’s belief that the listener will sympathize with his thoughts in the utterance or utterance itself is revealed in the sentence of the ‘-jan-(-잖-)’ and the rhetorical question. ‘geureonikka(그러니까)’, as mentioned before, ‘-nikka(-니까)’ makes the preceding interlocutor’s utterances already known. Therefore, ‘geureonikka(그러니까)’ is a suitable marker to satisfy the speaker’s beliefs and expectations in the ‘-jan-(-잖-)’ and the rhetorical question.