A method of heating asbestos containing materials and changing their structure from crystal fibrous to that deprived of fiber structure using an electromagnetic field is provided and is characterized by crumbling of utilized material. Crumbled material is being transported to microwave reactor. During transportation and the crumbling process, material chunks are being mixed with a heating facilitating agent. The device includes a utilized materials' crusher (1), crumbled material chunks's worm (2), heating facilitating agent's feeder (3) and microwave thermal reactor (4). The feeder (3) is adjoined to the crusher (1) and/or to the worm (2). The reactor (4) has a heating chamber (9) made of materials that do not absorb microwave radiation which is located at the transporter's (2) outlet.