A heat exchanger, comprising a housing and a core body accommodated in the housing, wherein the housing comprises a first body and a second body , the first body is made of metal, the second body is made of plastic, and the first body and the second body are connected to form a first cavity; the core body is accommodated in the first cavity, the core body is fixedly connected to the first body , the core body comprises a plurality of heat exchange pipes , the plurality of heat exchange pipes are stacked, a first fluid passage is formed between the plurality of heat exchange pipes , a second fluid passage is formed inside the plurality of heat exchange pipes , and the first fluid passage is not in communication with the second fluid passage; the heat exchanger further comprises a connecting block , the connecting block is fixed to the first body and the connecting block is located outside the first cavity, a first flow-through hole is provided in the connecting block , a second flow-through hole is provided in the first body , and the first flow-through hole and the second fluid passage are in communication by the second flow-through hole ; wherein the first body is in a flat-plate shape, the second body has a U-shaped tank portion , the first body covers at an open end of the tank portion of the second body and a connection between the first body and the second body is sealed; characterized in that an arc portion protruding outward is provided on a side plate of the second body , a first duct is formed between the arc portion and the core body, and a second hole in communication with the first duct is provided on the first body , wherein the second hole is in communication with the first fluid passage through the first duct. the core body is accommodated in the first cavity, the core body is fixedly connected to the first body , the core body comprises a plurality of heat exchange pipes , the plurality of heat exchange pipes are stacked, a first fluid passage is formed between the plurality of heat exchange pipes , a second fluid passage is formed inside the plurality of heat exchange pipes , and the first fluid passage is not in communication with the second fluid passage; the heat exchanger further comprises a connecting block , the connecting block is fixed to the first body and the connecting block is located outside the first cavity, a first flow-through hole is provided in the connecting block , a second flow-through hole is provided in the first body , and the first flow-through hole and the second fluid passage are in communication by the second flow-through hole ; wherein the first body is in a flat-plate shape, the second body has a U-shaped tank portion , the first body covers at an open end of the tank portion of the second body and a connection between the first body and the second body is sealed; characterized in that an arc portion protruding outward is provided on a side plate of the second body , a first duct is formed between the arc portion and the core body, and a second hole in communication with the first duct is provided on the first body , wherein the second hole is in communication with the first fluid passage through the first duct. <EOS>