A heat exchanger, comprising: a plurality of coolant tubes (2, 4, 6) having a longitudinal direction; and a plurality of fins (8, 10) contacting at least one of the plurality of coolant tubes (2, 4, 6), wherein each of the plurality of fins (8, 10) comprises: a plurality of fin parts (12, 14) spaced apart from each other; a first opening formed at a first side of each of the plurality of fin parts (12, 14); a second opening formed at a second side of each of the plurality of fin parts (12, 14); characterized in that each of the plurality of fins (8, 10) further comprises: a first protrusion provided at the first side of each of the plurality of fin parts (12, 14), contacting one of the plurality of coolant tubes (2, 4, 6); a second protrusion provided at the second side of each of the plurality of fin parts (12, 14), contacting another of the plurality of coolant tubes (2, 4, 6), a first fin part connecting part connecting the first side of neighboring ones of the plurality of fin parts (12, 14) with each other, whilst contacting said one of the plurality of coolant tubes (2, 4, 6); and a second fin part connecting part connecting the second side of next neighboring ones of the plurality of fin parts (12, 14) with each other, whilst contacting said another of the plurality of coolant tubes (2, 4, 6), wherein the first opening and the first fin part connecting part surround said one of the plurality of coolant tubes (2, 4, 6), and the second opening and the second fin part connecting part surround said another of the plurality of coolant tubes (2, 4, 6), wherein each of the first fin part connecting part and the second fin part connecting part includes a pair of contacting parts spaced apart from and parallel to each other, and wherein the plurality of coolant tubes (2, 4, 6) has a shape of a hollow straight pipe, and wherein each of the pair of contacting parts includes a curved surface that comes into surface contact with a portion of the plurality of coolant tubes (2, 4, 6). a plurality of coolant tubes (2, 4, 6) having a longitudinal direction; and a plurality of fins (8, 10) contacting at least one of the plurality of coolant tubes (2, 4, 6), wherein each of the plurality of fins (8, 10) comprises: a plurality of fin parts (12, 14) spaced apart from each other; a first opening formed at a first side of each of the plurality of fin parts (12, 14); a second opening formed at a second side of each of the plurality of fin parts (12, 14); a plurality of fin parts (12, 14) spaced apart from each other; a first opening formed at a first side of each of the plurality of fin parts (12, 14); a second opening formed at a second side of each of the plurality of fin parts (12, 14); characterized in that each of the plurality of fins (8, 10) further comprises: a first protrusion provided at the first side of each of the plurality of fin parts (12, 14), contacting one of the plurality of coolant tubes (2, 4, 6); a second protrusion provided at the second side of each of the plurality of fin parts (12, 14), contacting another of the plurality of coolant tubes (2, 4, 6), a first fin part connecting part connecting the first side of neighboring ones of the plurality of fin parts (12, 14) with each other, whilst contacting said one of the plurality of coolant tubes (2, 4, 6); and a second fin part connecting part connecting the second side of next neighboring ones of the plurality of fin parts (12, 14) with each other, whilst contacting said another of the plurality of coolant tubes (2, 4, 6), wherein the first opening and the first fin part connecting part surround said one of the plurality of coolant tubes (2, 4, 6), and the second opening and the second fin part connecting part surround said another of the plurality of coolant tubes (2, 4, 6), wherein each of the first fin part connecting part and the second fin part connecting part includes a pair of contacting parts spaced apart from and parallel to each other, and wherein the plurality of coolant tubes (2, 4, 6) has a shape of a hollow straight pipe, and wherein each of the pair of contacting parts includes a curved surface that comes into surface contact with a portion of the plurality of coolant tubes (2, 4, 6). a first protrusion provided at the first side of each of the plurality of fin parts (12, 14), contacting one of the plurality of coolant tubes (2, 4, 6); a second protrusion provided at the second side of each of the plurality of fin parts (12, 14), contacting another of the plurality of coolant tubes (2, 4, 6), a first fin part connecting part connecting the first side of neighboring ones of the plurality of fin parts (12, 14) with each other, whilst contacting said one of the plurality of coolant tubes (2, 4, 6); and a second fin part connecting part connecting the second side of next neighboring ones of the plurality of fin parts (12, 14) with each other, whilst contacting said another of the plurality of coolant tubes (2, 4, 6), wherein the first opening and the first fin part connecting part surround said one of the plurality of coolant tubes (2, 4, 6), and the second opening and the second fin part connecting part surround said another of the plurality of coolant tubes (2, 4, 6), wherein each of the first fin part connecting part and the second fin part connecting part includes a pair of contacting parts spaced apart from and parallel to each other, and wherein the plurality of coolant tubes (2, 4, 6) has a shape of a hollow straight pipe, and wherein each of the pair of contacting parts includes a curved surface that comes into surface contact with a portion of the plurality of coolant tubes (2, 4, 6).