The invention relates to a heat treatment process for disinfection of seeds from pathogens and other undesirable fungi and bacteria, the process being characterized by supply to the seeds non water-borne heat while regulating the treatment time and temperature with regard to the condition and moisture content of the seeds in such a way that the seeds are heated from outside and in, while evaporation of moisture from the surface of the seed, and owing to that, cooling of the same is prevented and no changes in the moisture content occur.