PURPOSE: To realize a vacuum dryer in which an efficiency of drying steps can be enhanced by employing a structure in which a work can be conveyed in and out of a vacuum drying chamber without returning the chamber to the atmospheric temperature.

CONSTITUTION: A supply material spare chamber 11 and a removed material spare chamber 13 are provided at both sides of a vacuum drying chamber 12 of a vacuum dryer 20, and gate mechanisms 14-17 are provided all in openings such as work delivery ports. An air flow supply passage 302 opened as a nozzle 301, a compressor 303 connected to the passage 302, and a first solenoid valve 305 for opening/closing the passage 302 are provided at the side of the chamber 11, and an air exhaust passage 307 opened as an air exhaust part 306 and a second solenoid valve 308 for opening/closing the passage 307 are provided at its bottom side.