A heat exchanger comprising: a plurality of refrigerant tubes through which a refrigerant flows, the refrigerant tubes being arranged in a plurality of rows; a first header on which a refrigerant inflow part is disposed, the first header being coupled to one side of the plurality of refrigerant tubes and comprising a first front part and a first rear part thereinside; a first partition part for partitioning the first front part and the first rear part of the first header ; a second header on which a refrigerant discharge part is disposed, the second header being coupled to the other side of the plurality of refrigerant tubes ; a second partition part for partitioning an inner space of the second header ; and a baffle coupled to the first or second partition part , the baffle guiding a flow of the refrigerant from the first or the second header to the plurality of refrigerant tubes , wherein the heat exchanger further comprises a guide hole formed at the first partition part for guiding the refrigerant from the first front part to flow toward the first rear part or to flow into the plurality of refrigerant tubes , wherein the refrigerant discharge part of the second header is located below the refrigerant inflow part of the first header , wherein the guide hole is defined in a position that is more adjacent to the refrigerant discharge part than the refrigerant inflow part with respect to a refrigerant passage defined from the refrigerant inflow part to the refrigerant discharge part , wherein the baffle comprises a plurality of baffles coupled to one side and the other side of the second partition part , and a plurality of through holes separated by the plurality of baffles are defined in the second partition part , and wherein a portion of the refrigerant in the first front part flows downward toward the plurality of front tubes and the rest of the refrigerant flows to the first rear part through the guide hole . a plurality of refrigerant tubes through which a refrigerant flows, the refrigerant tubes being arranged in a plurality of rows; a first header on which a refrigerant inflow part is disposed, the first header being coupled to one side of the plurality of refrigerant tubes and comprising a first front part and a first rear part thereinside; a first partition part for partitioning the first front part and the first rear part of the first header ; a second header on which a refrigerant discharge part is disposed, the second header being coupled to the other side of the plurality of refrigerant tubes ; a second partition part for partitioning an inner space of the second header ; and a baffle coupled to the first or second partition part , the baffle guiding a flow of the refrigerant from the first or the second header to the plurality of refrigerant tubes , wherein the heat exchanger further comprises a guide hole formed at the first partition part for guiding the refrigerant from the first front part to flow toward the first rear part or to flow into the plurality of refrigerant tubes , wherein the refrigerant discharge part of the second header is located below the refrigerant inflow part of the first header , wherein the guide hole is defined in a position that is more adjacent to the refrigerant discharge part than the refrigerant inflow part with respect to a refrigerant passage defined from the refrigerant inflow part to the refrigerant discharge part , wherein the baffle comprises a plurality of baffles coupled to one side and the other side of the second partition part , and a plurality of through holes separated by the plurality of baffles are defined in the second partition part , and wherein a portion of the refrigerant in the first front part flows downward toward the plurality of front tubes and the rest of the refrigerant flows to the first rear part through the guide hole . <EOS>