An air-conditioning apparatus comprising: a cabinet including therein a heat exchanger and a fan, having a lower surface with an opening, and installable to a ceiling; a square decorative panel larger than the opening of the cabinet, having an air inlet in a central part thereof, and installed to cover the opening of the lower surface of the cabinet; air outlets disposed at four places around the air inlet along four sides of the decorative panel; air direction vanes (5a to 5d) provided in the air outlets, and independently adjustable in angle for the respective air outlets; an infrared sensor capable of detecting a floor surface temperature for each of divided areas (A1 to A4) quartered in a circumferential direction; and a controller, wherein the infrared sensor is installed to one of four corners (C1 to C4) of the decorative panel, and configured such that a facing direction of an installation reference of the infrared sensor varies depending on each of four corners installed with the infrared sensor, and the controller is configured for controlling one of the air direction vanes (5a to 5d) so as to blow out an airflow toward a floor surface from one of the air outlets and the air-conditioning apparatus to perform a heating operation or a cooling operation, is configured for performing a determination to determine an installation position of the infrared sensor from the installation reference of the infrared sensor, characterized in that the controller is configured for performing said determination additionally from: one of the divided areas (A1 to A4) in which a temperature difference between the floor surface temperature before an operation of the one of the air direction vanes (5a to 5d) and the floor surface temperature during the operation of the one of the air direction vanes (5a to 5d) detected with the infrared sensor is the largest and equals or exceeds a specified value, and the installation reference of the infrared sensor, and is configured for making the one of the divided areas(A1 to A4) in which the temperature difference is the largest and equals or exceeds the specified value correspond to the one of the air direction vanes (5a to 5d) to be controlled. a cabinet including therein a heat exchanger and a fan, having a lower surface with an opening, and installable to a ceiling; a square decorative panel larger than the opening of the cabinet, having an air inlet in a central part thereof, and installed to cover the opening of the lower surface of the cabinet; air outlets disposed at four places around the air inlet along four sides of the decorative panel; air direction vanes (5a to 5d) provided in the air outlets, and independently adjustable in angle for the respective air outlets; an infrared sensor capable of detecting a floor surface temperature for each of divided areas (A1 to A4) quartered in a circumferential direction; and a controller, wherein the infrared sensor is installed to one of four corners (C1 to C4) of the decorative panel, and configured such that a facing direction of an installation reference of the infrared sensor varies depending on each of four corners installed with the infrared sensor, and the controller is configured for controlling one of the air direction vanes (5a to 5d) so as to blow out an airflow toward a floor surface from one of the air outlets and the air-conditioning apparatus to perform a heating operation or a cooling operation, is configured for performing a determination to determine an installation position of the infrared sensor from the installation reference of the infrared sensor, one of the divided areas (A1 to A4) in which a temperature difference between the floor surface temperature before an operation of the one of the air direction vanes (5a to 5d) and the floor surface temperature during the operation of the one of the air direction vanes (5a to 5d) detected with the infrared sensor is the largest and equals or exceeds a specified value, and the installation reference of the infrared sensor, and is configured for making the one of the divided areas(A1 to A4) in which the temperature difference is the largest and equals or exceeds the specified value correspond to the one of the air direction vanes (5a to 5d) to be controlled.