This device for inactivating and finely filtering viruses and microorganisms in a flow of air is intended for cleaning air or gas. The device includes a high voltage power supply (4) and the following components arranged in series in the direction of flow: a unit (1) for pre-treating a flow of air, a two-section inactivation chamber (2) and a precipitator (3). The pre-treating unit (1) consists of oppositely charged conductive filtering elements (7, 7′). The first conductive filtering element (7) in the direction of flow is in the form of a cylindrical electrode (6) and a plate (9) which is made of a current conductive, highly porous material and is positioned at a distance from the free end face of the cylindrical electrode (6). A needle electrode (8), electrically associated with the plate (9), is adjacent to said plate. The base of the cylindrical electrode is in the form of a plate (7) which is made of a conductive, porous and permeable material and is adjacent to a plate (5) made of a dielectric, highly porous permeable material. The needle electrode is disposed coaxially with the cylindrical electrode and the point of the needle electrode is oriented towards the dielectric plate. The cylindrical and needle electrodes are connected to opposite poles of the power supply. The device makes it possible to increase the operational efficiency of the device.