Abstract: A freeze drying apparatus comprises a heat-transfer medium container having heat-transfer medium inlet/outlet pipes, a plurality of tubes extending through the heat-transfer medium container from its lower plate to upper plate, a lower space formed beneath the heat-transfer medium container and being in communication with the tubes and a product liquid inlet/outlet conduit, an openable bottom lid defining the bottom of the lower space, an upper space formed above the upper plate of the heat-transfer medium container, a trap chamber being in communication with the upper space, pressure regulation lid means operable to airtightly cover part of the tubes at their upper ends, and a pressure regulation conduit with pressure regulation valve operable to regulate pressure in the tubes covered with the pressure regulation lid means.

Abstract: In the freeze drying method of the present invention, a predetermined amount of water is poured on the refrigerating/heating surface provided in the drying chamber, which surface is cooled to a temperature below 0.degree. C., so that an ice film is formed on the refrigerating/heating surface. After that, while the thus formed ice film is kept at a temperature below 0.degree. C., a liquid material is supplied to the surface of the ice film so that a frozen layer of the liquid material is formed on the surface of the ice film. Under such circumstances, a vacuum is produced in the drying chamber to conduct the freeze drying operation of the frozen material in a vacuum environment.