PURPOSE: To provide a vacuum drying device, capable of drying moisture after water washing, which is extremely hard to dry compared with fluorocarbon or the like employed for the washing of high technical products such as print substrates and the like so far, with the same speed as the speed of production so far.

CONSTITUTION: The title device is constituted of a conveyer 1, shifting works W1, a preheating means for the works W1 on the way of being shifted, single or a plurality of vacuum tanks 7, equipped with both of a heating means for works W2 thereafter and a conveying means 6 for shifting the works W2, and conveyer 12 for shifting the works W2 of thereafter again.