An outdoor unit of an air-conditioning apparatus, the outdoor unit comprising: a noise control system comprising: one or more reference sensors arranged near a noise source, the sensors being configured to pick up a noise source signal from the noise source; one or more control speakers configured to radiate a noise cancellation signal for canceling the noise source signal; one or more error sensors arranged in a noise cancellation field subject to noise cancellation by the noise cancellation signal, the error sensors being configured to pick up an acoustic signal of the noise cancellation field; an error scanning filter configured to generate the noise cancellation signal by employing adaptive signal processing based on an adaptive control algorithm from the noise source signal picked up by the reference sensors and from the acoustic signal of the noise cancellation field picked up by the error sensors; a housing that accommodates the noise source; and a guide member configured to radiate the noise source signal from the housing when the noise cancellation signal is not radiated from the control speakers; and a compressor disposed inside the housing; an intake fan configured to take air into the housing; and a heat exchanger configured to exchange heat with the air taken in, and characterized in that the guide member is frame-shaped and comprises a circumference surface and one or more sound openings located on said circumference surface, wherein the control speakers are arranged on the circumference surfaces at the positions where the sound openings are located, and are configured to radiate the noise cancellation signal to the inside of the guide member to create the noise cancellation field inside the guide member; wherein the guide member is disposed on an outer end of the heat exchanger at a position at the outside of the housing, where the air that is subject to heat exchange in the heat exchanger is discharged to the outside through the guide member, and the noise source includes the compressor and the intake fan. a noise control system comprising: one or more reference sensors arranged near a noise source, the sensors being configured to pick up a noise source signal from the noise source; one or more control speakers configured to radiate a noise cancellation signal for canceling the noise source signal; one or more error sensors arranged in a noise cancellation field subject to noise cancellation by the noise cancellation signal, the error sensors being configured to pick up an acoustic signal of the noise cancellation field; an error scanning filter configured to generate the noise cancellation signal by employing adaptive signal processing based on an adaptive control algorithm from the noise source signal picked up by the reference sensors and from the acoustic signal of the noise cancellation field picked up by the error sensors; a housing that accommodates the noise source; and a guide member configured to radiate the noise source signal from the housing when the noise cancellation signal is not radiated from the control speakers; and a compressor disposed inside the housing; an intake fan configured to take air into the housing; and a heat exchanger configured to exchange heat with the air taken in, and characterized in that the guide member is frame-shaped and comprises a circumference surface and one or more sound openings located on said circumference surface, wherein the control speakers are arranged on the circumference surfaces at the positions where the sound openings are located, and are configured to radiate the noise cancellation signal to the inside of the guide member to create the noise cancellation field inside the guide member; wherein one or more reference sensors arranged near a noise source, the sensors being configured to pick up a noise source signal from the noise source; one or more control speakers configured to radiate a noise cancellation signal for canceling the noise source signal; one or more error sensors arranged in a noise cancellation field subject to noise cancellation by the noise cancellation signal, the error sensors being configured to pick up an acoustic signal of the noise cancellation field; an error scanning filter configured to generate the noise cancellation signal by employing adaptive signal processing based on an adaptive control algorithm from the noise source signal picked up by the reference sensors and from the acoustic signal of the noise cancellation field picked up by the error sensors; a housing that accommodates the noise source; and a guide member configured to radiate the noise source signal from the housing when the noise cancellation signal is not radiated from the control speakers; and a compressor disposed inside the housing; an intake fan configured to take air into the housing; and a heat exchanger configured to exchange heat with the air taken in, and characterized in that the guide member is frame-shaped and comprises a circumference surface and one or more sound openings located on said circumference surface, wherein the control speakers are arranged on the circumference surfaces at the positions where the sound openings are located, and are configured to radiate the noise cancellation signal to the inside of the guide member to create the noise cancellation field inside the guide member; wherein the guide member is disposed on an outer end of the heat exchanger at a position at the outside of the housing, where the air that is subject to heat exchange in the heat exchanger is discharged to the outside through the guide member, and the noise source includes the compressor and the intake fan.