Abstract: A filter cleaning device for an air conditioner, includes: a filter through which an air flow passes, the filter having a filter surface; a brush that is contactable with the filter surface, removes particulate matter from the filter surface, and has a cylindrical shape; and a motor that rotates the brush in opposite directions to each other; a first comb-shaped member engaged with the brush; and a second comb-shaped member engaged with the brush, wherein the first and second comb-shaped members each have a length direction parallel to an axis of rotation of the brush and parallel to a width direction of each of the first and second comb-shaped members, and the first and second comb-shaped members are inclined away from each other in a cross-sectional view perpendicular to the axis of rotation of the brush.