The purpose of this study is to test the motivations for e-Learning service usage of smart device users. To do this, empirical data were collected by conducting a field survey with 382 smart-device based e-learners, and structural equation model was used for the purpose of analyzing the data acquired by the survey. A structural equation model was designed and constructed by such factors like usefulness, enjoyment, word-of-mouse(WOM) effect, and social interaction on e-Learning usage intention. In addition, social interaction has an influence on WOM effect. The results of the analysis are summarized as follows; first, usefulness, enjoyment, and WOM have direct effects on e-Learning usage intention. Second, social interaction not only has direct influence on e-Learning usage intention but also has indirect influence carried by WOM effect. The findings have significant implications which the study inquires into the factors for e-Learning usage motivations of smart-device based e-learners.