PURPOSE: To minimize the thermal resistance at various points from a vertical rotary element to refrigerant by providing the bottom plate of a vacuum container with a heat pipe, said heat pipe being equipped with a vaporizer which contacts the lower part of respective rotary elements and a condensing section which contacts the refrigerant of a cooling device.

CONSTITUTION: Multiple vertical rotary elements 5 are housed in the bottom plate 1 of a vacuum container 4 facing the interior of the vacuum container 4. The bottom plate 1 has a cooling device 7 for cooling the rotary elements, and also has a heat pipe 11, said heat pipe 11 having a vaporizing section 11a which contacts the lower part of respective rotary elements and a condensing section 11b which contacts the refrigerant of the cooling device 7. Therefore, the thermal resistance at various points from the rotary elements 5 to refrigerant can be minimized and the variance in the cooling effect among rotary elements 5 can be minimized by a relatively simple constitution without impairing the performance and reliability of the rotary elements 5.