An apparatus for manufacturing a heat exchanger including a refrigerant tube, the apparatus including a moving rod movable along a first direction; and a tube expansion body connected to the moving rod to be linearly movable along the first direction, the tube expansion body insertable into a tube base material of the refrigerant tub such that the tube base material is expanded outward when the tube expansion body is inserted into the tube base material of the refrigerant tube, wherein the tube expansion body includes a plurality of groove forming protrusions formed on an outer surface of the tube expansion body so as to extend along a direction inclined with respect to the first direction, the groove forming protrusions form a plurality of grooves on an inner surface of the tube base material, when the tube expansion body is moved to be inserted into the tube base material.