A combined cycle power generating device in which exhaust heat of a gas turbine reheats steam which is discharged from a high pressure chamber of a steam turbine so that the reheated steam is supplied to an intermediate-pressure chamber, thereby driving the steam turbine, the intermediate-pressure chamber comprising: a cooling steam inlet configured to provide cooling steam that has cooled the gas turbine to the intermediate-pressure chamber, wherein the cooling steam inlet is different from a reheat steam inlet for reheat steam that is reheated by the exhaust heat of the gas turbine, the cooling steam is supplied to the intermediate-pressure chamber without mixing the cooling steam with the reheat steam, and the cooling steam is supplied to the intermediate-pressure chamber to cool an intermediate pressure turbine rotor provided in the intermediate-pressure chamber; characterized in that the intermediate pressure chamber comprises: an intermediate pressure casing for supporting roots and tips of stator blades of a first stage stator cascade that is placed immediately behind the reheat steam inlet, as well as roots of stator blades (24b,24c) of a second stage stator cascade and the following stage stator cascades; and an intermediate pressure turbine rotor having a plurality of rotor cascades, the intermediate pressure turbine rotor being housed in the intermediate pressure casing, wherein the cooling steam inlet is configured by a cooling steam recovery pipe which is communicated to a space between the first stage stator cascade and a first stage rotor cascade, via a gap between the intermediate pressure turbine rotor and the intermediate pressure casing at a location where the intermediate pressure casing supports the stator blades of the first stage stator cascade. a cooling steam inlet configured to provide cooling steam that has cooled the gas turbine to the intermediate-pressure chamber, wherein the cooling steam inlet is different from a reheat steam inlet for reheat steam that is reheated by the exhaust heat of the gas turbine, the cooling steam is supplied to the intermediate-pressure chamber without mixing the cooling steam with the reheat steam, and the cooling steam is supplied to the intermediate-pressure chamber to cool an intermediate pressure turbine rotor provided in the intermediate-pressure chamber; characterized in that the intermediate pressure chamber comprises: an intermediate pressure casing for supporting roots and tips of stator blades of a first stage stator cascade that is placed immediately behind the reheat steam inlet, as well as roots of stator blades (24b,24c) of a second stage stator cascade and the following stage stator cascades; and an intermediate pressure turbine rotor having a plurality of rotor cascades, the intermediate pressure turbine rotor being housed in the intermediate pressure casing, an intermediate pressure casing for supporting roots and tips of stator blades of a first stage stator cascade that is placed immediately behind the reheat steam inlet, as well as roots of stator blades (24b,24c) of a second stage stator cascade and the following stage stator cascades; and an intermediate pressure turbine rotor having a plurality of rotor cascades, the intermediate pressure turbine rotor being housed in the intermediate pressure casing, wherein the cooling steam inlet is configured by a cooling steam recovery pipe which is communicated to a space between the first stage stator cascade and a first stage rotor cascade, via a gap between the intermediate pressure turbine rotor and the intermediate pressure casing at a location where the intermediate pressure casing supports the stator blades of the first stage stator cascade.