A heat exchanger comprising: a plurality of refrigerant tubes through which a refrigerant flows, the plurality of refrigerant tubes extending in a horizontal direction; a heatsink fin in which the plurality of refrigerant tubes are inserted, the heatsink fin being configured to heat-exchange the refrigerant with a fluid; a head (50, 100) coupled to sides of the plurality of refrigerant tubes to extend in a vertical direction, the head being arranged to allow the refrigerant to be distributed into the plurality of refrigerant tubes, and the head comprising a head body defining a flow space of the refrigerant and a tube coupling part to cover a front side of the head body to be coupled to the refrigerant tubes; a partition part arranged to horizontally partition at least one space of an inner space of the head (50, 100); and at least two or more through holes (452, 456), the at least two or more through holes guiding the refrigerant so that the refrigerant passes through the partition part to flow into the plurality of refrigerant tubes, the holes being vertically spaced apart from each other, characterized by further comprising a plurality of blocking ribs (458, 459) coupled to and below the partition part, the plurality of blocking ribs comprising a first blocking rib extending backward from a front surface of the head body and a second blocking rib extending forward from a rear surface of the head body, wherein the at least two or more through holes (452, 456) are defined in the rear part of the partition part (451, 455), and wherein the partition part comprises a first partition part received within the head (50, 100) and a second partition part received within the first partition part, and the first and second partition parts comprise a pipe defining a refrigerant flow space, and wherein the first blocking rib is coupled to one side of the second partition part, and the second blocking rib is coupled to the other side of the second partition part. a plurality of refrigerant tubes through which a refrigerant flows, the plurality of refrigerant tubes extending in a horizontal direction; a heatsink fin in which the plurality of refrigerant tubes are inserted, the heatsink fin being configured to heat-exchange the refrigerant with a fluid; a head (50, 100) coupled to sides of the plurality of refrigerant tubes to extend in a vertical direction, the head being arranged to allow the refrigerant to be distributed into the plurality of refrigerant tubes, and the head comprising a head body defining a flow space of the refrigerant and a tube coupling part to cover a front side of the head body to be coupled to the refrigerant tubes; a partition part arranged to horizontally partition at least one space of an inner space of the head (50, 100); and at least two or more through holes (452, 456), the at least two or more through holes guiding the refrigerant so that the refrigerant passes through the partition part to flow into the plurality of refrigerant tubes, the holes being vertically spaced apart from each other, characterized by further comprising a plurality of blocking ribs (458, 459) coupled to and below the partition part, the plurality of blocking ribs comprising a first blocking rib extending backward from a front surface of the head body and a second blocking rib extending forward from a rear surface of the head body, wherein the at least two or more through holes (452, 456) are defined in the rear part of the partition part (451, 455), and wherein the partition part comprises a first partition part received within the head (50, 100) and a second partition part received within the first partition part, and the first and second partition parts comprise a pipe defining a refrigerant flow space, and wherein the first blocking rib is coupled to one side of the second partition part, and the second blocking rib is coupled to the other side of the second partition part.