Abstract: In the vacuum drying of solid wood (2) and other wood-based products, the invention provides a method of achieving a better control of the drying process and a better heat economy than by the traditional methods of vacuum drying. This is achieved by completely evacuating the air from the space around the wood (2), and instead to fill the space (1) around the wood (2) with superheated water vapors (11). By maintaining a uniform pressure and temperature in all parts of the drying chamber (1) during the drying process, and controlling the temperature and the pressure of the superheated water vapors (11) in accordance with directives described in more detail, it is possible to control the dampness (MC) of the wood very precisely, and thereby to avoid damage to the wood (2) during drying.