The invention provides a gas turbine cooling system that efficiently cools a first-stage turbine wheel and the attachment portions of first-stage turbine blades. A gas turbine comprises: a compressor 1 for compressing air; a combustor 2 for combusting the air compressed by the compressor 1 with fuel; and a turbine 3 driven by the combustion gas from the combustor 2, the turbine 3 including a first-stage turbine wheel 12a having turbine blades 11a on an outer circumferential section thereof. A gas turbine cooling system comprises a group of impingement cooling holes 32, provided such that the compressed air 101 from the compressor 1 flows through a partition wall 16a separating the exit space 42 of the compressor 1 from the wheel space 43a located upstream of the turbine wheel 12a, for ejecting the compressed air 101 toward the turbine wheel 12a and the attachment portions of the turbine blades 11a.