To provide a sealing device of a turbine casing capable of easily adopting a seal ring pressed to the axial direction using a simple means without causing a bad influence upon space or strength.

In the sealing device of the turbine casing 1, the seal ring 3 pressed to the axial direction with a spring is placed between opposed wall surfaces in the axial direction of an outer casing 1 and an inner casing 2, a temporary stop means to temporary pull in and hold the seal ring against the energized force of the spring is provided when the outer casing 1 is assembled. The temporary stop means has plural pins 7 which are implanted at the back of the seal ring 3, the tip end of which penetrates through the casing wall and protrudes through a wall surface on an opposite side to the opposed wall surfaces, a hasp 8 which is engaged with the respective protruded parts to block the movement energized by the spring of the pins, and a wire 9 for releasing the engagement of the hasp 8 from the pins 7 from outside the outer casing by a remote control.