A microwave sterilizer for the sterilization of liquids contains a resonance chamber (1) and a process chamber (3) partially arranged inside this resonance chamber (1). The resonance chamber (1) is a body (2) and the process chamber (3) with a lid (4). The resonance chamber (1) contains the body (2), the process chamber (3) and the process chamber (3) lid (4). Magnetrons (5,6) are attached to the resonance chamber (1) body (2). Antennae (7) of the magnetrons (5,6) are put into the interior of the resonance chamber (1). A vessel (8) contains liquid material for sterilization. The resonance chamber (1) body (2) upper flange (11) surrounds the cylindrical process chamber (3) and the contact of this flange (11) with the wall of the process chamber (3) is sealed by means of peripheral seal (12).
