To prevent a noxious substance, e.g. dioxin, from being discharged at the time of treating a radiator by composing a header plate at the end of a radiator body and a tank mounted thereon of a same metallic material.

A tank 4 made of a metal, e.g. aluminum, is mounted through an O-ring 3 on a header plate 2 made of a metal, e.g. aluminum, at the end of a radiator body 1, e.g. a radiator. When the header plate 2 is coupled with the tank 4, an elastic body, i.e., the O-ring 3, is mounted on an annular groove 11 and the outward flange 14 of the tank 4 is mounted thereon. The header plate 2 and the tank 4 are made of different metals in order to prevent corrosion. The radiator can be treated without separating the header plate 2 from the tank 4 through dismantling and no noxious substance, e.g. dioxin, is generated when it is incinerated as a whole.