An air conditioner comprising: a heat exchanger including a refrigerant path divided into a plurality of unit paths (20, 30); a path switch part that connects at least two of the plurality of unit paths (20, 30) in parallel to one another in heating operation or switches at least two of the plurality of unit paths to be connected in series to one another in cooling operation; a first parallel connection path that connects one sides of the at least two of the plurality of unit paths (20, 30) in parallel to one another so that a refrigerant flowing into the heat exchanger flows into the at least two of the plurality of unit paths (20, 30) connected in parallel in the heating operation; and a second parallel connection path that connects the other sides of the at least two of the plurality of unit paths (20, 30) in parallel to one another so that the refrigerant passing through the at least two of the plurality of unit paths (20, 30) connected in parallel is discharged to the second parallel connection path in the heating operation; and a series connection path that connects the at least two of the plurality of unit paths (20, 30) in series to one another so that the refrigerant passing through one of the at least two of the plurality of unit paths (20, 30) is passed to an entrance side of another unit path connected in series in the cooling operation, characterized in that the air conditioner further comprises: at least two distributors (51, 52) that are respectively provided to correspond to the at least two unit paths (20, 30) on the first parallel connection path; and at least two headers (61, 62) that are respectively provided to correspond to the at least two unit paths (20, 30) on the second parallel connection path, wherein a portion of the refrigerant passes the first distributor, the first unit path, and the first header, and the other portion of the refrigerant passes the second distributor, the second unit path, the second header, the second parallel connection path, and the first header in the heating operation, and wherein the refrigerant passes through the first header, the first unit path, the first distributor, the series connection path, the second header, the second unit path, and the second distributor successively in the cooling operation. a heat exchanger including a refrigerant path divided into a plurality of unit paths (20, 30); a path switch part that connects at least two of the plurality of unit paths (20, 30) in parallel to one another in heating operation or switches at least two of the plurality of unit paths to be connected in series to one another in cooling operation; a first parallel connection path that connects one sides of the at least two of the plurality of unit paths (20, 30) in parallel to one another so that a refrigerant flowing into the heat exchanger flows into the at least two of the plurality of unit paths (20, 30) connected in parallel in the heating operation; and a second parallel connection path that connects the other sides of the at least two of the plurality of unit paths (20, 30) in parallel to one another so that the refrigerant passing through the at least two of the plurality of unit paths (20, 30) connected in parallel is discharged to the second parallel connection path in the heating operation; and a series connection path that connects the at least two of the plurality of unit paths (20, 30) in series to one another so that the refrigerant passing through one of the at least two of the plurality of unit paths (20, 30) is passed to an entrance side of another unit path connected in series in the cooling operation, characterized in that the air conditioner further comprises: at least two distributors (51, 52) that are respectively provided to correspond to the at least two unit paths (20, 30) on the first parallel connection path; and at least two headers (61, 62) that are respectively provided to correspond to the at least two unit paths (20, 30) on the second parallel connection path, wherein a portion of the refrigerant passes the first distributor, the first unit path, and the first header, and the other portion of the refrigerant passes the second distributor, the second unit path, the second header, the second parallel connection path, and the first header in the heating operation, and wherein the refrigerant passes through the first header, the first unit path, the first distributor, the series connection path, the second header, the second unit path, and the second distributor successively in the cooling operation. at least two distributors (51, 52) that are respectively provided to correspond to the at least two unit paths (20, 30) on the first parallel connection path; and at least two headers (61, 62) that are respectively provided to correspond to the at least two unit paths (20, 30) on the second parallel connection path, wherein a portion of the refrigerant passes the first distributor, the first unit path, and the first header, and the other portion of the refrigerant passes the second distributor, the second unit path, the second header, the second parallel connection path, and the first header in the heating operation, and wherein the refrigerant passes through the first header, the first unit path, the first distributor, the series connection path, the second header, the second unit path, and the second distributor successively in the cooling operation.