PURPOSE: To improve the rate of operation without lowering the quality of articles to be treated by installing a casing, in which a plurality of containers can be moved in connecting condition, a sealing device which seals the places between the outer surfaces of the containers and the inner surfaces of the casing, and an exhauster exhausts the inside of the casing in steps through a plurality of exhaust ducts.

CONSTITUTION: Containers 2 holding articles 1 to be dried are charged from the charging part of a vacuum treater into the inside of a casing 3 and transferred into the inside of the casing in connecting condition by a drive unit. While the containers 2 are successively transferred, at the section of an exhaust duct 4a the pressure is reduced to about 400Torr, for instance, and the containers are further transferred and at the part of an exhaust duct 4b the pressure is reduced to about 150Torr, for instance, and further at a vacuum treating room 3a the pressure is reduced to about 10Torr. During the time when the containers 2 are transferred on a conveyor 7 the articles 1 to be dried held in this containers are heated by a heat source such as a dielectric heating device 8, etc., and vacuum-dried in this room 3a. The containers 2 holding the vacuum-dried articles 1 are further transferred and in contrast with the course when the containers are charged, the pressure is successively being recovered in steps as 10Torr, 150Torr, 400Torr, and the atmospheric pressure and then the containers are discharged in the air.