In a gas turbine in which a seal member seals a gap between a transition piece and a nozzle end wall in a turbine first stage, the transition piece and the nozzle end wall has a seal groove. The seal member includes a hook portion that slides in the turbine radial direction with respect to the flange and a seal plate portion inserted in the groove. The groove and the portion are configured to include a surface contact region in which a surface of the groove and the portion are in surface contact with each other, a non-contact region disposed on a side closer to the transition piece than the region, and a hole provided at the portion so as to face the surface in the groove across a gap in the region.