To provide a glass ceramic substrate having improved resistance to a plating liquid, which is produced while the firing temperature at a temperature of ≤950°C is maintained, thereby adverse effects on substrate strength and dimensions are suppressed.

In a glass ceramic substrate, which is obtained by forming via conductors and a wiring film in green sheets, each containing a glass component and an inorganic filler, then laminating a pltirality of the green sheets, and firing the laminated sheets at 700 to 950°C, a glass ceramic film having high resistance to a plating liquid and thickness of 3 to 15 μm, preferably 5 to 10 μm is provided on the outermost layer of the glass ceramic substrate mentioned above.