The present invention provides a hot vacuum drying device applied for a flexible substrate. By respectively improving the first support pin (5) and the second support pin (6) of the hot vacuum drying device to be an insertion structure or a layer jacket structure, which can accelerate heat conduction to make a temperature difference between a contact part of the substrate (7) with the first support pin (5) or the second support pin (6) and a non-contact part of the substrate (7) with the first support pin (5) or the second support pin (6) decrease and to make heating uniform, and thus to reduce pin muras caused by the support pins, and to allow an appropriate increase in the amount of the support pins in a middle zone for reducing the film unevenness due to sagging of the substrate.