Provided is a constant-temperature device which comprises conveyance mechanism and which can operate stably over a long period of time even when installed in an atmosphere of a sterilization gas having strong oxidative properties, such as hydrogen peroxide gas, or a high temperature environment during dry-heat sterilization operations. A drive unit for a rotatably operated specimen table (10) on which a specimen is placed, in an incubation chamber, is arranged outside of the incubation chamber, and the drive-force from the drive unit is transmitted by means of magnetic coupling. Furthermore, ring-shaped seal packing (22), in which a lip (24) is formed, is arranged above and below a base plate (13) provided to the specimen plate (10), and a seal plate (23) is arranged along the entire perimeter of the base plate (13) at the portion which makes contact with the lip (24), thus a bearing (17) and/or a drive portion are isolated from high-temperature atmospheres and in-chamber atmospheres having strong oxidative properties, preventing damage due to high temperatures or sterilization gas.