Provided is a method for production of adamantane which enables producing a high-purity adamantane at low cost and with high efficiency by using effectively trimethylenenorbornane contained in a heavy raffinate heavy and having conventionally been no use other than fuels and the like, and which enables alleviating poisoning of a catalyst used in isomerization and corrosion of devices, whereby an industrially advantageous adamantane can be produced. In addition, the process for producing adamantane including an isomerization process of isomerizing trimethylenenorbornane contained in a raffinate obtained from a platfinate is characterized by including a water-washing removal process of removing sulfolane in a trimethylenenorbornane concentrate to be supplied in the isomerization process by water-washing.