An outdoor unit for an air-conditioning apparatus, having a compressor, a top cover configured to cover an upper surface of the compressor, and a side cover configured to cover a side of the compressor and a side of the top cover, the side cover including a rectangular cutout portion formed in a part of an upper end of the side cover. The outdoor unit has a non-water-absorbent draining element disposed across from a central portion of the top cover to a bottom portion of the cutout portion, and tilts down from the central portion of the top cover toward the bottom portion of the cutout portion.