Recently, a number of foreign researches have note the importance of mother tongue use in second language classroom, but there have been an active researches on Korean language education nor on the effects of using mother tongue. To analyze mother tongue"s function, experiment were conducted through the classroom observation. This experiment was conducted on the subjects consisting of Chinese learners whose native language were identical. The result from the experiment were analyzed as follows. First, learner"s mother tongue function is condition-oriented ideas such as helping students understand instructions, making use of culturally loaded words, and humor. Second, learner"s mother tongue function is as a bottom up language focused ideas such as translation of vocabulary, explaining of grammar, checking comprehension, and translation. Third, learner"s mother tongue function is as top down language focused ideas such as scaffolding for cognitively challenging material. Therefore, this study will present anopportunity to examine the effects of use of learner"s mother tongue. And through the use of learner"s mother tough, positive effect on the leaner"s affective factor.