Gas turbine rotor blade tip loss is reduced and loss caused by leakage of working fluid through gap between members constituting an annular flow passage is reduced. Turbine (AT) of a gas turbine (GT) constituting a combined cycle plant (CC) is supported to a turbine casing (4) to be expandable or contractible in turbine shaft (32) radial direction. First blade ring (41) corresponds to first stage turbine stator blades (TS1) and rotor blades (TR1) and comprises a first heating medium flow passage (41P) for steam circulation therein. Second blade ring (42) corresponds to second stage turbine stator blades (TS2) and rotor blades (TR2) and comprises a second heating medium flow passage (42P) for steam circulation therein. Further provided is a communication member (45) for connecting the first blade ring (41) and second blade ring (42) to each other and for communicating the first heating medium flow passage (41P) and second heating medium flow passage (42P) with each other.