Jaialdi is the most important ethnic festival for Basque diaspora in the world, celebrated in Boise, Idaho. Jaialdi 2015 was held in the last week of July, 2015, at the multiple locations in Boise. The main site was the Basque Block. This is just a block on the Grove Street, but an important memorial place for the Basque people, because of the existence of ex-boarding houses, handball court piloteak, the Basque Museum and Cultural Center, and especially the Basque Center Euskaldunak. This is a core place for community activity of the Basque people in Boise. In the period of Jaialdi 2015, a lot of Basque people living not only in the American West but also in the American Continents got together at this place, and they reconfirmed intensive and wide spread network among them. In this point, it can be said that Jaialdi operates itself as an instrument to reinforce their network. But this is not only the matter of the network of Basque Diasporas. In the case of Jaialdi 2015, about one tenth of visitors came from the Basque Country. The place of origin of immigrants still maintains strong relation with the festival space in Boise. The geographical origin of the Basque people and their worldwide diaspora function just like a transnational social space linking tightly the both of them.