An annular shroud surrounding tip ends of turbine blades is fitted on an inner peripheral surface of an open end of a turbine case. In order to prevent the shroud from being dropped off in an axial direction by a retaining part provided on a retaining ring fitted on an outer peripheral surface of the open end of the turbine case, an annular groove formed in the outer peripheral surface of the turbine case and an annular groove formed in an inner peripheral surface of the retaining ring are opposed to each other, and a connection wire is inserted so as to straddle the two annular grooves, thereby connecting the retaining ring to the turbine case. Accordingly, it is possible to easily perform attachment/detachment of the retaining ring with respect to the turbine case only by inserting the connection wire into or pulling it out from the two annular grooves, thereby facilitating maintenance of the shroud and the turbine blades. Therefore, this can improve ease of attachment/detachment of the retaining ring retaining the shroud of a gas turbine engine to the turbine case.