PURPOSE: To increase peeling strength after plating with Cu, Ni, and Au, to improve the peeling strength after water spray, and to improve resistance to the corrosion from edge, by conducting Cr/Cu-Cu or Ti/Cu-Cu metallization on a ceramic substrate.

CONSTITUTION: In a bell jar 7 are arranged a ceramic substrate 1 to be treated, a heater 8, a boat 9 contg. metallizing metal Cr (or Ti), a boat 10 contg. Cu, and a shutter 11 placed between the substrate 1 and the boats 9, 10. The bell jar 7 is evecuated and ceramic substrate 1 is preheated by the heater 8. An alloy film of Cr (or Ti)-Cu, which is composed of Cr (or Ti) and Cu in a ratio of 10:50W90:10 and of a thickness several Wtens of , is formed by metallization with the shutter 11 opened. The shutter 11 is once closed, and opened once again to metallize Cu film 3. The substrate is plated in addn. with Cu, Ni, or Au on the films described above.