In the present invention, there is disclosed a decontamination method of solid materials by thermal desorption in situ b making use of microwave energy, wherein the invented method is characterized in that solid contaminated material is subjected in-situ to the action of microwave pulses in a time interval in the range of 0.5 to 100 seconds within a sealed openings connected to a condensation device and hollowed-out at a distance of 0.5 to 5 m from each other onto a surface and a depth corresponding to the place of decontamination. Apparatus for making the above-described decontamination method comprises an applicator (2) in the form of a hollow container put inside a perforated jacket (6) for placing into the opening in the contaminated material, whereby the upper end of the applicator (2) is connected to a microwave generator and the space extending between the applicator (2) and the jacket (6) is connected to the condensation and separation device.