This paper describes an investigation of an outbreak of foot-and-mouth disease (FMD) in Republic of Korea in January 2010. In this paper, we investigated introduction to the index farm from overseas countries, transmission from index farm to other outbreak farms. The introduction factors were divided direct, indirect factors or airborne spread factor. Based on the epidemiological data, clinical information and other data, in these introduction factors, it was likely that outbreak of FMD in index farm was due to international goods or employees from overseas countries (including China). There were other suggested causes in index farm. But it was less likely that outbreak of FMD in index farm have occurred by other causes. The transmission factors from index farm to other farms were also divided direct, indirect factors or airborne spread factor. In these transmission factors it was possible to make assumptions from index farm to other outbreak farms that the FMD virus was transmitted through animal treatment, persons concerned and persons (who were) attended farmers’ assembly.