An air conditioner comprising: a refrigeration cycle; wherein the refrigeration cycle includes: a compressor having a variable operation frequency; a four-way valve for switching between heating and cooling; an outdoor heat exchanger for switchably serving as a condenser or an evaporator; a first expansion valve; and an indoor heat exchanger for switchably serving as an evaporator or a condenser; the compressor, the four-way valve, the outdoor heat exchanger, the first expansion valve, and the indoor heat exchanger are sequentially connected, in a loop form, to one another, the air conditioner is configured to change an air conditioning capacity by changing an operation frequency of the compressor by a controller in accordance with an air conditioning load determined by a temperature difference between a set temperature set by a room temperature setting unit and a suction temperature of indoor air detected by an indoor room temperature detector, the indoor heat exchanger is divided into a first heat exchange area and a second heat exchange area, the first heat exchange area and the second heat exchange area are connected in series via a second expansion valve, and the first heat exchange area and the second heat exchange area are disposed to overlap each other in an air flow direction, and (i) the controller is configured to throttle the second expansion valve when the operation frequency of the compressor is a minimum operation frequency and the air conditioning capacity is excessive for the determined air conditioning load, or, (ii) when a difference between a suction temperature of indoor air to be sucked into the indoor heat exchanger and a set temperature for being set by a remote controller is less than or equal to a predetermined value, the controller variably controls a valve opening degree of the first expansion valve or a number of rotations of an outdoor fan included in the outdoor heat exchanger. a refrigeration cycle; wherein the refrigeration cycle includes: a compressor having a variable operation frequency; a four-way valve for switching between heating and cooling; an outdoor heat exchanger for switchably serving as a condenser or an evaporator; a first expansion valve; and an indoor heat exchanger for switchably serving as an evaporator or a condenser; a compressor having a variable operation frequency; a four-way valve for switching between heating and cooling; an outdoor heat exchanger for switchably serving as a condenser or an evaporator; a first expansion valve; and an indoor heat exchanger for switchably serving as an evaporator or a condenser; the compressor, the four-way valve, the outdoor heat exchanger, the first expansion valve, and the indoor heat exchanger are sequentially connected, in a loop form, to one another, the air conditioner is configured to change an air conditioning capacity by changing an operation frequency of the compressor by a controller in accordance with an air conditioning load determined by a temperature difference between a set temperature set by a room temperature setting unit and a suction temperature of indoor air detected by an indoor room temperature detector, the indoor heat exchanger is divided into a first heat exchange area and a second heat exchange area, the first heat exchange area and the second heat exchange area are connected in series via a second expansion valve, and the first heat exchange area and the second heat exchange area are disposed to overlap each other in an air flow direction, and (i) the controller is configured to throttle the second expansion valve when the operation frequency of the compressor is a minimum operation frequency and the air conditioning capacity is excessive for the determined air conditioning load, or, (ii) when a difference between a suction temperature of indoor air to be sucked into the indoor heat exchanger and a set temperature for being set by a remote controller is less than or equal to a predetermined value, the controller variably controls a valve opening degree of the first expansion valve or a number of rotations of an outdoor fan included in the outdoor heat exchanger. (i) the controller is configured to throttle the second expansion valve when the operation frequency of the compressor is a minimum operation frequency and the air conditioning capacity is excessive for the determined air conditioning load, or, (ii) when a difference between a suction temperature of indoor air to be sucked into the indoor heat exchanger and a set temperature for being set by a remote controller is less than or equal to a predetermined value, the controller variably controls a valve opening degree of the first expansion valve or a number of rotations of an outdoor fan included in the outdoor heat exchanger.