An air-conditioning device comprising an indoor unit (10a, 10b) that includes: a heat exchanger (1a, 1b) configured for refrigerant flowing through the heat exchanger, a refrigerant sensor (3a, 3b) configured to detect any refrigerant leaking from the heat exchanger (1a, 1b) into air, a fan (6a, 6b) configured to send air to the heat exchanger (1a, 1b), and a controller (7a, 7b) configured to control operation of the refrigerant sensor (3a, 3b) and the fan (6a, 6b), wherein the controller (7a, 7b) is configured to stop operation of the fan (6a, 6b) and make the refrigerant sensor (3a, 3b) detect any refrigerant, characterized by the controller (7a, 7b) being configured to stop operation of the fan (6a, 6b) when running time of the indoor unit (10a, 10b) is within a predetermined fixed-time control interval; wherein the indoor unit (10a, 10b) further includes a remote control (8a, 8b) for use to set a volume of a room (5a, 5b) in which the indoor unit (10a, 10b) is to be placed; and the controller (7a, 7b): prestores reference value data, which represents relationships between volumes of rooms (5a, 5b) and fixed-time control intervals, and is configured to determine the fixed-time control interval based on the volume of the room (5a, 5b) set via the remote control (8a, 8b) and the reference value data; the fixed-time control interval is shorter than time taken until refrigerant concentration in the room (5a, 5b) in which the indoor unit (10a, 10b) is placed reaches an explosive level; the fixed-time control interval is determined from reference value data, prestored in the air-conditioning device, based on initial settings; and the reference value data is a digitized form of a relationship between the volume of the room (5a, 5b) and time taken for the refrigerant concentration in the room (5a, 5b) to reach a minimum explosive concentration. a heat exchanger (1a, 1b) configured for refrigerant flowing through the heat exchanger, a refrigerant sensor (3a, 3b) configured to detect any refrigerant leaking from the heat exchanger (1a, 1b) into air, a fan (6a, 6b) configured to send air to the heat exchanger (1a, 1b), and a controller (7a, 7b) configured to control operation of the refrigerant sensor (3a, 3b) and the fan (6a, 6b), wherein the controller (7a, 7b) is configured to stop operation of the fan (6a, 6b) and make the refrigerant sensor (3a, 3b) detect any refrigerant, characterized by the controller (7a, 7b) being configured to stop operation of the fan (6a, 6b) when running time of the indoor unit (10a, 10b) is within a predetermined fixed-time control interval; wherein the indoor unit (10a, 10b) further includes a remote control (8a, 8b) for use to set a volume of a room (5a, 5b) in which the indoor unit (10a, 10b) is to be placed; and the controller (7a, 7b): prestores reference value data, which represents relationships between volumes of rooms (5a, 5b) and fixed-time control intervals, and is configured to determine the fixed-time control interval based on the volume of the room (5a, 5b) set via the remote control (8a, 8b) and the reference value data; prestores reference value data, which represents relationships between volumes of rooms (5a, 5b) and fixed-time control intervals, and is configured to determine the fixed-time control interval based on the volume of the room (5a, 5b) set via the remote control (8a, 8b) and the reference value data; the fixed-time control interval is shorter than time taken until refrigerant concentration in the room (5a, 5b) in which the indoor unit (10a, 10b) is placed reaches an explosive level; the fixed-time control interval is determined from reference value data, prestored in the air-conditioning device, based on initial settings; and the reference value data is a digitized form of a relationship between the volume of the room (5a, 5b) and time taken for the refrigerant concentration in the room (5a, 5b) to reach a minimum explosive concentration.