To provide an excellent effect including the reduction of facility cost, the improvement of reliability and the reduction of a facility area, compared with a system for utilizing an external inter-cooler, by installing a gas cooling device inside at least one of a easing and a stationary blade so as to cool gases at a pressure rise process.

A coolant having pressure boosted with a pump 11 flows in the part of a casing 1A between the first-stage and the second-stage moving blades 13a and 13b, and a coolant passage 6a formed inside a stationary blade 3a via a pipeline 12. Also, the coolant after the coolant passage 6a first flows in an upper pipe passage 14a laid outside the easing 1A and then flows to the next coolant passage 6b. Furthermore, the coolant after the passage 6b flows in an upper pipeline 14b similarly formed outside the casing 1A and then flows in the next coolant passage 6c, thereby being discharged from an upper pipeline 12a. As a result, gases having pressure raised with the moving blades 13a to 13d are effectively cooled with the coolant flowing in the coolant passages 6a to 6c formed within the easing 1A and the stationary blades 3a to 3d.