An air conditioner comprising: ∘ a heat exchanger (42, 52, 23) that causes refrigerant to pass therethrough while changing the state of the refrigerant, the heat exchanger comprising: ∘ a plurality of fins that are arranged side-by-side in a plate thickness direction; and ∘ a pipe that penetrates the plurality of fins from the plate thickness direction and branches at least two times such that the number of pipes through which the refrigerant passes increases between a first inlet/outlet and second inlets/outlets (S1 to S4) of a fin group comprising the plurality of fins, wherein the pipe branches just two times between the first inlet/outlet and the second inlets/outlets (S1 to S4), ∘ a fan (28, 28a, 43, 43a, 53, 53a) that supplies a flow of air to the heat exchanger (42, 52, 23); characterized in that the air conditioner further comprises ∘ a branch memory that stores data relating to branching positions of the pipes in the heat exchanger; ∘ a state quantity detector (32, 33, 34, 36, 44, 55) that detects state quantities of the refrigerant flowing through the pipe; and ∘ a controller that is configured to control the air volume of the fan such that the state of the refrigerant before the branching positions is different from the state of the refrigerant after the branching positions on the basis of values that the state quantity detector has detected and the data stored in the branch memory. ∘ a heat exchanger (42, 52, 23) that causes refrigerant to pass therethrough while changing the state of the refrigerant, the heat exchanger comprising: ∘ a plurality of fins that are arranged side-by-side in a plate thickness direction; and ∘ a pipe that penetrates the plurality of fins from the plate thickness direction and branches at least two times such that the number of pipes through which the refrigerant passes increases between a first inlet/outlet and second inlets/outlets (S1 to S4) of a fin group comprising the plurality of fins, wherein the pipe branches just two times between the first inlet/outlet and the second inlets/outlets (S1 to S4), ∘ a fan (28, 28a, 43, 43a, 53, 53a) that supplies a flow of air to the heat exchanger (42, 52, 23); characterized in that the air conditioner further comprises ∘ a branch memory that stores data relating to branching positions of the pipes in the heat exchanger; ∘ a state quantity detector (32, 33, 34, 36, 44, 55) that detects state quantities of the refrigerant flowing through the pipe; and ∘ a controller that is configured to control the air volume of the fan such that the state of the refrigerant before the branching positions is different from the state of the refrigerant after the branching positions on the basis of values that the state quantity detector has detected and the data stored in the branch memory. ∘ a plurality of fins that are arranged side-by-side in a plate thickness direction; and ∘ a pipe that penetrates the plurality of fins from the plate thickness direction and branches at least two times such that the number of pipes through which the refrigerant passes increases between a first inlet/outlet and second inlets/outlets (S1 to S4) of a fin group comprising the plurality of fins, wherein the pipe branches just two times between the first inlet/outlet and the second inlets/outlets (S1 to S4), ∘ a fan (28, 28a, 43, 43a, 53, 53a) that supplies a flow of air to the heat exchanger (42, 52, 23); ∘ a branch memory that stores data relating to branching positions of the pipes in the heat exchanger; ∘ a state quantity detector (32, 33, 34, 36, 44, 55) that detects state quantities of the refrigerant flowing through the pipe; and ∘ a controller that is configured to control the air volume of the fan such that the state of the refrigerant before the branching positions is different from the state of the refrigerant after the branching positions on the basis of values that the state quantity detector has detected and the data stored in the branch memory.