Providing a sealing mechanism provided with bellows-joints, the sealing mechanism being manufactured without surplus time and labor; thereby, the natural frequencies regarding the sealing mechanism surrounding a to-be-sealed shaft body are easily handled. Around a rotor shaft 26 of a steam turbine 10, between an outer turbine casing 12 and a gland 32, a sealing mechanism 40A is provided; the sealing mechanism is provided with an outer bellows-joint 46 and an inner bellows-joint 48, both the joints being arranged without mutual contact; the left and right ends of the outer bellows-joint 46 are gas-tightly connected to the outermost end periphery of the end flange 42 and the end flange 44, respectively; the left and right ends of the inner bellows-joint 48 are gas-tightly connected to the innermost end periphery of the end flange 42 and the end flange 44, respectively. Positioning both the bellows-joints can be easily performed.