Abstract: The invention relates to a method for cleaning the filter plates of a suction drier, which suction drier (20) comprises a tank (13) for the slurry to be suction dried, in connection to which tank there rotates one or several filter disks formed of the said filter plates (14), on the surface or surfaces of which filter plates (14) there is collected and dried, owing to the suction flow passing through the filter plates (14), a filter cake, which is scraped or otherwise removed from the surface or surfaces of the filter plates. For the cleaning of the porous structure and surfaces of the said filter plates (14), there is arranged, in the tank (13) of the slurry to be filtered, under the liquid surface (11), mainly in the surface water area, an ultrasonic vibrator or vibrators (10), whereto ultrasonic electric power is fed from an ultrasonic generator (22). The cleaning with the ultrasonic vibrator or vibrators (10) is carried out esentially immediately after scraping.