A filter cleaning device (1) has an improved structure which is capable of effectively cleaning dust in a filter (10) used in an air conditioner. The filter cleaning device (1) includes: a filter (10); a brush unit (20) movably installed at one side of the filter to separate dust from the filter (10); a brush movement unit (30) configured so that the brush unit (20) is movable along the filter (10); and brush guides (40) installed at two sides of the brush unit (20) to guide a movement of the brush unit (20). Each of the brush guides (40) includes: a first guide groove (41) formed so that the brush unit (20) is moved to be in contact with the filter (1'); and a second guide groove (43) formed so that the brush unit (20) is moved to be separated from the filter (10).