A constant-temperature device comprising: a thermostatic chamber having a closed space and walls surrounding said closed space; a rotating magnetic field generation means (7, 8) for generating a rotating magnetic field having a rotation axis in a vertical direction from an underside of a floor face of a bottom portion of the walls to the closed space through the floor face; a specimen plate for arranging a plurality of specimen shelves each saving a container storing a specimen for culturing or testing; and a magnet plate having a plurality of magnets to be driven by the rotating magnetic field generation means (7, 8), the magnets being magnetically coupled with the rotating magnetic field transmitted through the walls of the thermostatic chamber, characterized in that the constant-temperature device further comprises a base plate detachably screwed on the floor face through brackets in the closed space of the thermostatic chamber, the base plate being supported by support blocks each having a resin-made pad at a portion where the support block comes in contact with the floor face, said pad receiving a load from above, wherein the base plate has a bearing rotatably supporting a rotating shaft having a rotation axis that coincides with the rotation axis of the rotating magnetic field, the rotating shaft being supported in the vertical direction by the bearing of the base plate, wherein the specimen plate is connected to an upper side of the rotating shaft above the bearing, and wherein the magnet plate is connected to the rotating shaft below the bearing to rotate the rotating shaft in accordance with the rotating magnetic field. a thermostatic chamber having a closed space and walls surrounding said closed space; a rotating magnetic field generation means (7, 8) for generating a rotating magnetic field having a rotation axis in a vertical direction from an underside of a floor face of a bottom portion of the walls to the closed space through the floor face; a specimen plate for arranging a plurality of specimen shelves each saving a container storing a specimen for culturing or testing; and a magnet plate having a plurality of magnets to be driven by the rotating magnetic field generation means (7, 8), the magnets being magnetically coupled with the rotating magnetic field transmitted through the walls of the thermostatic chamber, characterized in that the constant-temperature device further comprises a base plate detachably screwed on the floor face through brackets in the closed space of the thermostatic chamber, the base plate being supported by support blocks each having a resin-made pad at a portion where the support block comes in contact with the floor face, said pad receiving a load from above, wherein the base plate has a bearing rotatably supporting a rotating shaft having a rotation axis that coincides with the rotation axis of the rotating magnetic field, the rotating shaft being supported in the vertical direction by the bearing of the base plate, wherein the specimen plate is connected to an upper side of the rotating shaft above the bearing, and wherein the magnet plate is connected to the rotating shaft below the bearing to rotate the rotating shaft in accordance with the rotating magnetic field.