Teachers' beliefs are a major factor in the effective use of new technology in teaching and learning. Recently, smart mobile devices (SMDs) such as smartphones, smart pads and tablet computers have been responsible for introducing broad innovations into the education field as Self-directed, Motivated, Adaptive, Resources-enriched, Technology embedded education in South Korea. Teachers' beliefs and technology acceptance concerning SMDs in South Korea can be either a facilitator or a barrier to the use of SMDs in the classroom. The purpose of this study is to investigate the factors of teachers' beliefs concerning SMDs, and to examine teachers' technology acceptance of SMDs in their lessons. To address these goals, 378 primary and 390 secondary teachers participated in a survey with a 25-item paired adjective questionnaire and a 12-item technology acceptance questionnaire. A series of exploratory and confirmatory factor analyses and multiple regressions were applied for the statistical analysis. The results indicate that teachers' beliefs were consistently revealed the five factors of "immediacy," "interest," "interactivity," "instability" and "inconvenience." Regarding the effect of the technology acceptance of SMDs on teachers' beliefs, the factors of instability, inconvenience and interactivity strongly related to the perceived usefulness and ease of use of SMDs. This finding indicates that teachers' beliefs that SMDs are unstable or uncomfortable can be the main barrier to the use of technology in the classroom.