In 1910, when the Korean Empire was annexed by Japan, the traditional Lee dynasty collapsed. And in 1911, Xinhai Revolution collapsed the Qing dynasty in China. Republic of China was founded by the revolution, and 2011 is the 100th anniversary of the ROC. ROC supported the provisional government of the Republic of Korea in Chinese mainland and Korean independence movement, and since Republic of Korea’s foundation in 1948, Republic of China had been the most important anti-communist ally. ROK severed diplomatic relationship with ROC on August 24, 1992, as the former normalized relationship with People’s Republic of China. Since severance of relationship , ROK does not recognize national status of ROC, calls it ‘Taiwan’ instead of ‘Republic of China, and ROK-ROC relationship is maintained as ‘highest unofficial relationship.’ The 100 years of ROK-ROC relationship reflects not only change and conflict of histories of Korea and China, but also upheaval of east Asia in the 20th century, division of both countries and ideological problem of modern history. This also gives an issue that both countries must solve on how to overcome the national division of Korea and China and how to lead the mutual relationship in the 21st century. Here, history of relationship between Korea and ROC is reviewed, and status of ROK-ROC relationship and the factors influencing on it are analyzed.