PURPOSE: To effectively dry a packaging board, etc., by heating in a vacuum atmosphere the packaging board, etc., which are washed clean water and to which the clean water is adhered, and further vibrating them.

CONSTITUTION: An air flow device 5 blows off water droplets due to clean water adhering to a packaging board P received from a washing process, and a vibrator 7 vibrates the packaging board P to resonate water droplets adhering to the board and parts. As the inside of a vacuum container 2 is evacuated, a washing fluid adhering to the packaging board P is evaporated and is robbed of its vaporization heat but is supplied with heat from a far-infrared heater 6. Further, the vibrator 7 provides a resonance frequency to resonate the washing fluid on the packaging board P and the same adhering to gaps among the parts, whereby the washing fluid is pushed spread in a thin and wide manner and jumps out from the narrow gaps and is directly irradiated with far-infrared rays for promotion of evaporation.