While being transferred in substantially horizontal state along a predetermined path of transfer by a conveyer means, a substrate plate is dried by a jet of compressed air which is spurted out from a slit-like mouth of an air knife nozzle crosswise of the entire width of the substrate plate and at a predetermined angle of incidence with respect to a drying surface of the substrate plate to scrape off a liquid. The angle of incidence of jet air is made shallower as soon as the substrate on the conveyer means comes to a point of entry to an air blasting zone and is made deeper at latest when the substrate plate comes to a position immediately before a point of disengagement from the air blasting zone.