An outdoor unit for an air conditioner, comprising: a casing; a compressor installed in the casing and compressing refrigerant; an accumulator installed in the casing and separating liquid refrigerant from refrigerant that flows into the compressor; and a soundproof member absorbing or insulating noise generated while the compressor operates and placed to surround the compressor, wherein the soundproof member includes: a first soundproof member absorbing or insulating noise by forming an outer surface of the soundproof member; and a second soundproof member (421, 423) provided in the first soundproof member and absorbing noise in a relatively lower-frequency band than the first soundproof member, characterised in that the first soundproof member surrounds the compressor and the accumulator, the second soundproof member (421, 423) being provided in multiple number having a plate shape to cross each other within the first soundproof member, and each of the second members (421, 423) partitioning a space surrounded by the first soundproof member into a zone where the compressor is positioned and a zone where the accumulator is positioned, and absorbing noise in a relatively lower-frequency band than the first soundproof member. a casing; a compressor installed in the casing and compressing refrigerant; an accumulator installed in the casing and separating liquid refrigerant from refrigerant that flows into the compressor; and a soundproof member absorbing or insulating noise generated while the compressor operates and placed to surround the compressor, wherein the soundproof member includes: a first soundproof member absorbing or insulating noise by forming an outer surface of the soundproof member; and a second soundproof member (421, 423) provided in the first soundproof member and absorbing noise in a relatively lower-frequency band than the first soundproof member, characterised in that the first soundproof member surrounds the compressor and the accumulator, the second soundproof member (421, 423) being provided in multiple number having a plate shape to cross each other within the first soundproof member, and each of the second members (421, 423) partitioning a space surrounded by the first soundproof member into a zone where the compressor is positioned and a zone where the accumulator is positioned, and absorbing noise in a relatively lower-frequency band than the first soundproof member. a first soundproof member absorbing or insulating noise by forming an outer surface of the soundproof member; and a second soundproof member (421, 423) provided in the first soundproof member and absorbing noise in a relatively lower-frequency band than the first soundproof member, characterised in that the first soundproof member surrounds the compressor and the accumulator, the second soundproof member (421, 423) being provided in multiple number having a plate shape to cross each other within the first soundproof member, and each of the second members (421, 423) partitioning a space surrounded by the first soundproof member into a zone where the compressor is positioned and a zone where the accumulator is positioned, and absorbing noise in a relatively lower-frequency band than the first soundproof member.