A heat exchanger with a core part; an upper reinforcing plate which is disposed on the upper side of the core part in the height direction and in which a first fixing/matching section is formed; a pair of lateral reinforcing plates disposed on both sides of the core part in the longitudinal direction, the upper side of at least one of the two lateral reinforcing plates being coupled to the first fixing/matching section of the upper reinforcing plate, and a second fixing/matching section being formed on the lower side of each of the lateral reinforcing plates; and a lower reinforcing plate disposed on the lower side of the core part in the height direction, and both sides of which are coupled to the second fixing/matching sections of the pair of lateral reinforcing plates, wherein each of components can be correctly positioned, and thus productivity and assemblability are improved.