This article measured and analyzed the indoor radon concentrations at one university building inGyeongju, Republic of Korea, to investigate if there is any relationship between earthquakes and indoorradon concentration. Since 12 September 2016, when two 5.1 and 5.8 magnitude earthquakes occurred,hundreds of aftershocks affected Gyeongju until January 2017. The measurements were made at theground floor of the Energy Engineering Hall of Dongguk University in Gyeongju over a period betweenFebruary 2016 and January 2017.