Seonreung is the tomb of Seong-jong (A.D. 1457~1494), the 9th king of Joseon Dynasty (1392-1910) and his second queen Jeonghyeon-wanghu (1462~1530). We obtained dendrochronological dates of Jeongjagak (ceremonial hall) of Seonreung. It was known first built in 1495 and reconstructed in October 1706, We obtained tree-ring dates of 20 wood elements (beams, pillars, truss posts, cant strips, roof boards and roof loaders). Their outermost rings were dated from 1630 to 1705. The dates of bark rings in four elements were A.D. 1705 with completed latewoods, indicating that these woods were cut some time between the autumn of 1705 and spring of 1706. The results confirmed the reconstruction date Jeongjagak of Seonreung in 1706, suggesting that there was not so long period for wood drying or storage, i.e., less than 6 months. The dates of outermost rings prior to 1705 in other elements indicated that some outer rings of these elements were removed during wood processing. Tree-ring dating proved that the present Jeongjagak of Seonreung had been well preserved for more than 300 years.