An air conditioning system comprising: a heat exchanger, comprising: a first header which has an inner chamber, two second headers, each of which has an inner chamber, first heat exchange pipes which are connected between one of said two second headers and said first header and are in fluid communication with the inner chamber of said one of said two second headers and the inner chamber of said first header, and second heat exchange pipes which are connected between the other one of said two second headers and said first header and are in fluid communication with the inner chamber of said the other one of said two second headers and the inner chamber of said first header, wherein said heat exchanger is bent at a first bent portion between said the other one of said two second headers and said first header, so that the other one of said two second headers is higher or lower than said first header, characterized in that the air conditioning system further comprises: a casing in which said heat exchanger is located, and a partition wall which divides an inner space of the casing into a first partition and a second partition, such that the first heat exchange pipes are located in the first partition and the second heat exchange pipes are located in the second partition; and said partition wall is located at the first header and thermally insulates the first partition from the second partition; a condensation fan configured to blow air from an outside of a room to the second heat exchange pipes to condense a refrigerant in the heat exchanger; and an evaporation fan configured to blow air from an inside of the room to the first heat exchange pipes to evaporate the refrigerant in the heat exchanger; wherein evaporation and condensation are completed in the same heat exchanger and a height difference between the other one of said two second headers and said first header provides a motive power source for internal circulation to complete the two cycles of evaporation and condensation of the refrigerant. a heat exchanger, comprising: a first header which has an inner chamber, two second headers, each of which has an inner chamber, first heat exchange pipes which are connected between one of said two second headers and said first header and are in fluid communication with the inner chamber of said one of said two second headers and the inner chamber of said first header, and second heat exchange pipes which are connected between the other one of said two second headers and said first header and are in fluid communication with the inner chamber of said the other one of said two second headers and the inner chamber of said first header, a first header which has an inner chamber, two second headers, each of which has an inner chamber, first heat exchange pipes which are connected between one of said two second headers and said first header and are in fluid communication with the inner chamber of said one of said two second headers and the inner chamber of said first header, and second heat exchange pipes which are connected between the other one of said two second headers and said first header and are in fluid communication with the inner chamber of said the other one of said two second headers and the inner chamber of said first header, wherein said heat exchanger is bent at a first bent portion between said the other one of said two second headers and said first header, so that the other one of said two second headers is higher or lower than said first header, characterized in that the air conditioning system further comprises: a casing in which said heat exchanger is located, and a partition wall which divides an inner space of the casing into a first partition and a second partition, such that the first heat exchange pipes are located in the first partition and the second heat exchange pipes are located in the second partition; and said partition wall is located at the first header and thermally insulates the first partition from the second partition; a condensation fan configured to blow air from an outside of a room to the second heat exchange pipes to condense a refrigerant in the heat exchanger; and an evaporation fan configured to blow air from an inside of the room to the first heat exchange pipes to evaporate the refrigerant in the heat exchanger; a casing in which said heat exchanger is located, and a partition wall which divides an inner space of the casing into a first partition and a second partition, such that the first heat exchange pipes are located in the first partition and the second heat exchange pipes are located in the second partition; and said partition wall is located at the first header and thermally insulates the first partition from the second partition; a condensation fan configured to blow air from an outside of a room to the second heat exchange pipes to condense a refrigerant in the heat exchanger; and an evaporation fan configured to blow air from an inside of the room to the first heat exchange pipes to evaporate the refrigerant in the heat exchanger; wherein evaporation and condensation are completed in the same heat exchanger and a height difference between the other one of said two second headers and said first header provides a motive power source for internal circulation to complete the two cycles of evaporation and condensation of the refrigerant.