This research aims to show the relationship between ancient Korean and Japanese court dances through analysing of the gagaku structure and finding out the origin of the gagaku clans. The terms in the togaku like Kogaku and Shingaku also allude that some Shingaku pieces could be transmitted though Korea. The origin of the gagaku clans also suggests the connection between gagaku and ancient Korea. It is important that togaku clans as well as komagaku clans are associated with Korea. This indicates some togaku pieces were transmitted from Korea, and alludes to the birth of gagaku being associated with Korean performances.