This study aims to investigate the developmental stages of Korean epistemic modality. The spontaneous utterances of children at 31~43 months of age were recorded in interaction with their mothers for about one year, then transcribed and analyzed. The results show that morpheme acquisition of the modality markers will be preceded to their meanings in developmental processes of Epistemic Modality. The frequent use of the modality markers ‘-지’, ‘-네’, ‘-겠-’, ‘-구나’ was shown in all of 4 children, which means their morphological acquisition was in stable stage. We also investigated the acquisition process of the epistemic modality’s meaning in relation to contextual interpretations. As a result, we found that the modality markers ‘-지’, ‘-네’, ‘-겠-’ were used in diverse contexts as in adult language, whereas the modality markers ‘-구나’, ‘-더-’ were used in limited contexts. We concluded that the acquisition of the epistemic modality’s meaning was still incomplete in this age.