An air-conditioning apparatus comprising: refrigerant, a refrigeration cycle adapted for circulating the refrigerant; an indoor unit accommodating at least an indoor heat exchanger of the refrigeration cycle, the indoor unit being configured for being disposed in an indoor space; and a control unit configured to control the indoor unit, a refrigerant detection unit disposed in the vicinity of an air inlet opening and configured to detect a concentration of refrigerant in the air around the refrigerant detection unit, and to output a resulting detection signal to the control unit, wherein the control unit is configured to determine whether refrigerant leaks based on the detection signal from the refrigerant detection unit, the refrigerant being a flammable refrigerant with a density greater than a density of air under atmospheric pressure, the indoor unit including an air-sending fan, an air inlet for having air of the indoor space sucked therethrough, and an air outlet for having the air sucked in through the air inlet blown out therethrough, the air outlet being located above the air inlet, the air outlet being provided on a front face or a side face of a housing of the indoor unit, wherein the control unit is configured to activate the air-sending fan when leakage of the refrigerant is detected to gradually disperse the refrigerant to a lower space that is a space in the indoor space located at a height equal to or below a height Ho [m] representing a value suitable for being a height of an upper end of the air outlet above a floor surface of the indoor space, when M [kg] represents an amount of charge of the refrigerant in the refrigeration cycle, LFL [kg/m 3] represents a lower flammable limit of the refrigerant, and A [m 2] represents a value suitable for being a floor area of the indoor space,, the amount of charge M, the lower flammable limit LFL, the floor area A, and the height Ho satisfying a relationship of M < LFL × A × Ho, wherein the indoor unit is of a floor-standing type and the height Ho of the air outlet above the floor surface corresponds to the height dimension of the indoor unit from its bottom surface, wherein the floor area A is the applicable floor area specified by the specifications of the air-conditioning apparatus or the indoor unit. refrigerant, a refrigeration cycle adapted for circulating the refrigerant; an indoor unit accommodating at least an indoor heat exchanger of the refrigeration cycle, the indoor unit being configured for being disposed in an indoor space; and a control unit configured to control the indoor unit, a refrigerant detection unit disposed in the vicinity of an air inlet opening and configured to detect a concentration of refrigerant in the air around the refrigerant detection unit, and to output a resulting detection signal to the control unit, wherein the control unit is configured to determine whether refrigerant leaks based on the detection signal from the refrigerant detection unit, the refrigerant being a flammable refrigerant with a density greater than a density of air under atmospheric pressure, the indoor unit including an air-sending fan, an air inlet for having air of the indoor space sucked therethrough, and an air outlet for having the air sucked in through the air inlet blown out therethrough, the air outlet being located above the air inlet, the air outlet being provided on a front face or a side face of a housing of the indoor unit, wherein the control unit is configured to activate the air-sending fan when leakage of the refrigerant is detected to gradually disperse the refrigerant to a lower space that is a space in the indoor space located at a height equal to or below a height Ho [m] representing a value suitable for being a height of an upper end of the air outlet above a floor surface of the indoor space, when M [kg] represents an amount of charge of the refrigerant in the refrigeration cycle, LFL [kg/m 3] represents a lower flammable limit of the refrigerant, and A [m 2] represents a value suitable for being a floor area of the indoor space,, the amount of charge M, the lower flammable limit LFL, the floor area A, and the height Ho satisfying a relationship of M < LFL × A × Ho, wherein the indoor unit is of a floor-standing type and the height Ho of the air outlet above the floor surface corresponds to the height dimension of the indoor unit from its bottom surface, wherein the floor area A is the applicable floor area specified by the specifications of the air-conditioning apparatus or the indoor unit.