Electric filter (1) to be used for purification of combustion gases by means of separation based on an high voltage electric field, consisting of a conduit (5), where there are electrodes (6) to be positively charged while the walls of the conduit (5) are to be negatively charged, whereby the electric filter (1) is also provided with means for removal of accumulated scale from the walls of the conduit (5). The electric filter (1) consist of an outer jacket (3) and a central inner jacket (4) so that the conduit (5) is formed between the outer jacket (3) and the inner jacket (4), and the cleaning apparatus comprises a trough (11) that can be moved up and down in the conduit (5).